Systematic review: Exposure to pets and risk of asthma and asthma-like symptoms

Exposure to cats: update on risks for sensitization and allergic diseases

Cats are the pets most commonly implicated in the etiology of asthma and allergic disease. However, systematic reviews have concluded that there is a lack of evidence to support the idea that cat exposure in early life increases the risk of allergic disease. Indeed, it appears most likely that cat exposure is protective against allergic diseases. Recent large prospective studies have shown that living with a cat during childhood, especially during the first year of a child's life, could be protective. However, any advice given to the parents should also incorporate how new acquisition of cats can affect other family members, especially those who are already sensitized. Research is urgently needed to determine whether the suggested impact of acquisition of cats in adult life is modified by the person's childhood pet ownership, to help parents who seek advice on whether or not to get a cat.

Does pet ownership in infancy lead to asthma or allergy at school age? Pooled analysis of individual participant data from 11 European birth cohorts

OBJECTIVE

To examine the associations between pet keeping in early childhood and asthma and allergies in children aged 6-10 years.

DESIGN

Pooled analysis of individual participant data of 11 prospective European birth cohorts that recruited a total of over 22,000 children in the 1990s. EXPOSURE DEFINITION: Ownership of only cats, dogs, birds, rodents, or cats/dogs combined during the first 2 years of life. OUTCOME DEFINITION: Current asthma (primary outcome), allergic asthma, allergic rhinitis and allergic sensitization during 6-10 years of age.

DATA SYNTHESIS

Three-step approach: (i) Common definition of outcome and exposure variables across cohorts; (ii) calculation of adjusted effect estimates for each cohort; (iii) pooling of effect estimates by using random effects meta-analysis models.

RESULTS

We found no association between furry and feathered pet keeping early in life and asthma in school age. For example, the odds ratio for asthma comparing cat ownership with "no pets" (10 studies, 11489 participants) was 1.00 (95% confidence interval 0.78 to 1.28) (I(2) = 9%; p = 0.36). The odds ratio for asthma comparing dog ownership with "no pets" (9 studies, 11433 participants) was 0.77 (0.58 to 1.03) (I(2) = 0%, p = 0.89). Owning both cat(s) and dog(s) compared to "no pets" resulted in an odds ratio of 1.04 (0.59 to 1.84) (I(2) = 33%, p = 0.18). Similarly, for allergic asthma and for allergic rhinitis we did not find associations regarding any type of pet ownership early in life. However, we found some evidence for an association between ownership of furry pets during the first 2 years of life and reduced likelihood of becoming sensitized to aero-allergens.

CONCLUSIONS

Pet ownership in early life did not appear to either increase or reduce the risk of asthma or allergic rhinitis symptoms in children aged 6-10. Advice from health care practitioners to avoid or to specifically acquire pets for primary prevention of asthma or allergic rhinitis in children should not be given.

Allergic predisposition modifies the effects of pet exposure on respiratory disease in boys and girls: the seven northeast cities of China (SNECC) study

BACKGROUND

The relationship between pet exposure and the respiratory disease in childhood has been a controversial topic, much is still unknown about the nature of the associations between pet exposure and children's respiratory health stratified by gender and allergic predisposition. The objective of the present study was to assess the relationship between pet exposure and respiratory symptoms in Chinese children, and to investigate the modified effects of gender and allergic predisposition on such relationship.

METHODS

31,049 children were selected from 25 districts of 7 cities in Northeast China in 2009. Information on respiratory health and exposure to home environmental factors was obtained via a standard questionnaire designed by the American Thoracic Society.

RESULTS

Children with an allergic predisposition were found to have more frequent exposure to pets than those without an allergic predisposition (18.5% vs. 15.4%). In children without an allergic predisposition, pet exposure was associated with increased susceptibility to respiratory symptoms/diseases, with girls being more susceptible than boys. No association was found between pet exposure and respiratory symptoms/diseases in boys with an allergic predisposition. In girls with an allergic predisposition, association was found between doctor-diagnosed asthma and pet exposure of their mother during pregnancy (adjusted odds ratio (ORs)=2.03; 95% confidence interval (CI): 1.01-4.33), and their current pet exposure (ORs=1.37; 95%CI: 1.00-1.88).

CONCLUSIONS

Pet exposure in children without an allergic predisposition was associated with increased susceptibility to respiratory disease, with girls being more susceptible than boys.

Rhinoconjunctivitis prevalence and associated factors in school children aged 6-7 and 13-14 years old in Bogota, Colombia

OBJECTIVE

Allergic rhinitis is one of the most frequent chronic diseases among children. The objective of the study was to assess the prevalence of rhinoconjunctivitis and determine clinical, social and environmental associated factors, among school children aged 6-7 years and adolescents aged 13-14 years in Bogotá, Colombia.

METHODS

We used ISAAC (International Study of Asthma and Allergies in Childhood) phase III study methodology and questionnaire for design and data collection, and we did a secondary analysis of these data. The sample consisted of 3830 registers from adolescents between 13 and 14 years old and 3256 registers from children between 6 and 7 years.

RESULTS

The prevalence of rhinoconjunctivitis symptoms in the last year was 17.2% (95% CI, 15.9-18.5) in children vs. 24.9% (95% CI, 23.6-26.3) in adolescents. In both groups there was a female predominance in children (17.8% vs. 16.5%), and in the teenagers group (28.0% vs. 21.4%), though the differences were not statistically significant. The factors associated with rhinoconjunctivitis in the group of 6-7 years where: asthma [OR 3.9; (95% CI, 2.8-5.4)], atopic dermatitis [OR 2.3; (95% CI, 1.7-3.1)], use of acetaminophen in the last year [OR 2.6; (95% CI, 1.4-4.9)], use of antibiotics in the first year of live [OR 1.7; (95% CI, 1.3-2.3)], higher maternal education [OR 1.5; (95% CI, 1.0-2.3)] and cesarean delivery [OR 1.6; (95% CI, 1.2-2.1)]. Among the 13-14 year age-group, factors associated with rhinoconjunctivitis included: asthma [OR 2.6; (95% CI, 2.0-3.4)], atopic dermatitis [OR 1.8; (95% CI, 1.4-2.3)], use of acetaminophen in the last year [OR 1.8; (95% CI, 1.4-2.4)], consumption of fast-food three times or more per week [OR 1.5; (95% CI, 1.2-2.0), ever smoked [OR 1.4; (95% CI, 1.2-1.7)] and meat consumption was protective factor [OR 0.7; (95% CI, 0.5-0.9)].

CONCLUSION

In both studied groups, the estimated prevalence of rhinoconjunctivitis symptoms was relatively high. Future in-depth research is needed to assess the complex interactions between allergic rhinoconjunctivitis symptoms and social and environmental factors.

Impact of environmental controls on childhood asthma

Exposure to allergens early in life can lead to sensitization and the development of childhood asthma. It is thought that increased exposure with the advent of modern housing is likely contributing to the rise in prevalence of childhood asthma during the past few decades. The progression from allergen exposure to sensitization and asthma development has been noted with respect to dust mites, pets, cockroach, mouse, mold, tobacco smoke, endotoxin, and air pollution, although some have found a protective effect with pet and endotoxin exposure. Recent studies have shown that allergen remediation may be beneficial in reducing asthma morbidity and development, although there is also some evidence to the contrary. Examples of allergen remediation that have been studied include the use of dust mite-impermeable covers, high-efficiency particulate air filtration, integrated pest management, home repairs, ventilation improvement, and pet removal. Several multifaceted, randomized controlled trials have shown that reducing multiple early allergen exposures with environmental controls is associated with a decreased risk of asthma.

Perinatal cat and dog exposure and the risk of asthma and allergy in the urban environment: a systematic review of longitudinal studies

BACKGROUND

The literature is contradictory concerning pet exposure and the risk of development of asthma and other allergic diseases. Using longitudinal studies, we aimed to systematically review the impact of pet ownership in the critical perinatal period as a risk factor for allergies in childhood.

METHODS

Medline database was searched for urban cohort studies with perinatal exposure to cats and/or dogs and subsequent asthma or allergic disease.

RESULTS

Nine articles, comprising 6498 participants, met inclusion criteria. Six found a reduction in allergic disease associated with perinatal exposure to dogs or, cats or dogs. One study found no association. Two found increased risk only in high-risk groups.

CONCLUSION

Longitudinal studies in urban populations suggest that perinatal pets, especially dogs, may reduce the development of allergic disease in those without a family history of allergy. Other unmeasured factors such as pet-keeping choices in allergic families may be confounding the association seen in these high-risk families, and further study is required.

Prevalence of asthma and allergies in 13- to 14-year-old adolescents and the frequency of risk factors in carriers of current asthma in Taubaté, São Paulo, Brazil

BACKGROUND

The objectives of this study were to determine the prevalence of asthma and allergies in 13- to 14-year-old adolescents in the city of Taubaté, São Paulo, Brazil using the INTERNATIONAL STUDY OF ASTHMA AND ALLERGIES IN CHILDHOOD (ISAAC) questionnaire and to describe the presence of risk factors in current asthma carriers.

METHODS

We used a cross-sectional study involving 920 adolescents who completed the ISAAC questionnaire and answered additional questions regarding smoking and the presence of pets and/or insects at home.

RESULTS

The mean prevalence rate of "current asthma" was 15.3% and "asthma ever" was 6.8%. The mean prevalence rate of "current rhinitis" was 36.6% and "rhinitis ever" 37.6%. The prevalence of "eczema ever" was 16.2%. The frequency of active smoking was low (0.7%), and the presence of indoor animals (34%) and of insects (55.1%) was high.

CONCLUSIONS

The prevalence of "current asthma" was twice as high as that of "asthma ever". There was no association between risk factors studied and current asthma.

Rhinovirus-associated wheeze during infancy and asthma development

Rhinovirus is commonly associated with bronchiolitis - only second to RSV during the first year life. The prevalence of HRV-bronchiolitis may be very high in predisposed infants. HRV diagnosis is almost exclusively based on PCR, which detects respiratory infections with or without symptoms. Two immunologic factors, interferon responses and atopy, have been associated with susceptibility to HRV-bronchiolitis in multiple studies. The current data supports the hypothesis that susceptibility to HRV-bronchiolitis is likely to be an early manifestation of biased immune responses, which are linked to both decreased viral defence and atopic airway inflammation. Prospective studies have consistently shown that early wheezing associated with HRV infection is closely associated with recurrent wheezing and the development of asthma in children. Collectively, these studies suggest that HRV infection in wheezing children could serve as a clinically useful marker for early identification of asthma prone children. The findings to date provide the rationale for future studies to incorporate rhinovirus illnesses into asthma risk indices.

Characterization of the asthmatic population of St. Vincent and the Grenadines: asthma severity levels and atopic sensitization

BACKGROUND

The developing country of St. Vincent and the Grenadines (SVG) reported a 4.5-fold increase in wheezing incidence between 1986 and 2002. It is unknown whether aeroallergens play a significant role in asthma in SVG.

OBJECTIVE

The objective of the study is to investigate the importance of aeroallergens and the association between age and persistence of asthma into adulthood. Methods. Subjects were recruited from the National Asthma Clinic. Asthma was diagnosed in 525 participants and severity levels assigned according to the National Heart, Lung, and Blood Institute guidelines. Participants were separated into three age groups [≤6 years (n=176), 7-18 years (n=164), and ≥19 years (n=185)]. Skin testing was performed on 171 participants to dust mite, cat, dog, cockroach, pollens, and mold. Age of asthma onset was obtained.

RESULTS

Persistent asthma was diagnosed in 235 participants (44.8%) and increased with increasing age group (p<.0001). Atopy was identified in 121/171 (70.8%) participants and was significantly higher in persistent asthma (p<.004). A significant positive association was seen between atopy and age group (p<.0004) in participants with intermittent asthma but not in participants with persistent asthma. The most common allergen among the atopic participants was house dust mite (93.4%), followed by cockroach (47.9%). Adult participants reporting asthma onset in adulthood were less atopic than those whose asthma developed ≤18 years of age (p<.05).

CONCLUSIONS

The predominance of asthma with atopy in SVG implicates a role for atopy in the sudden rise in asthma cases. This asthma characteristic and the increase in persistent asthma with age in SVG are similar to those reported in the developed countries.

[Relationships between indoor allergens, sensitization, and allergic asthma and rhinitis symptoms]

INTRODUCTION

There is a strong and consistent association between immediate hypersensitivity, asthma and exposure to allergens. However, the role that the inhaled allergen plays and the timing of events related to sensitization are still controversial.

BACKGROUND

Information obtained by studies of the follow-up of cohorts underlines the fact that there is no continuum between specific IgE responses and the development of childhood asthma. Allergic rhinitis and asthma result from a complex and multifactorial interaction between genetic factors, exposure to allergens, and many biological or chemical co-factors. However, when the child is exposed to an allergen, sensitization to the allergen is a risk factor for childhood asthma and severity of the disease.

CONCLUSIONS AND VIEWPOINTS

Despite numerous epidemiological studies, the association and links between atopy, allergens, environment, sensitization and allergic rhinitis and/or asthma remain difficult to evaluate and poorly understood. Complementary studies are also necessary for the standardization of therapeutic strategies.

Do questions reflecting indoor air pollutant exposure from a questionnaire predict direct measure of exposure in owner-occupied houses?

Home characteristic questions are used in epidemiological studies and clinical settings to assess potentially harmful exposures in the home. The objective of this study was to determine whether questionnaire-reported home characteristics can predict directly measured pollutants. Sixty home inspections were conducted on a subsample of the 2006 population-based Toronto Child Health Evaluation Questionnaire. Indoor/outdoor air and settled dust samples were analyzed. Mean Fel d 1 was higher (p < 0.0001) in homes with a cat (450.58 μg/g) versus without (22.28 μg/g). Mean indoor NO(2) was higher (p = 0.003) in homes with gas stoves (14.98 ppb) versus without (8.31 ppb). Self-reported musty odours predicted higher glucan levels (10554.37 μg/g versus 6308.58 μg/g, p = 0.0077). Der f 1 was predicted by the home's age, but not by reports of carpets, and was higher in homes with mean relative humidity > 50% (61.30 μg/g, versus 6.24 μg/g, p = 0.002). Self-reported presence of a cat, a gas stove, musty odours, mice, and the home's age and indoor relative humidity over 50% predicted measured indoor levels of cat allergens, NO(2), fungal glucan, mouse allergens and dust mite allergens, respectively. These results are helpful for understanding the significance of indoor exposures ascertained by self-reporting in large epidemiological studies and also in the clinical setting.

Childhood asthma and early life exposure to indoor allergens, endotoxin and beta(1,3)-glucans

BACKGROUND

Divergent results have been reported regarding early life exposure to indoor environmental agents and the risk of asthma and allergic sensitization later in life.

OBJECTIVE

To assess whether early exposure to indoor allergens, beta(1,3)-glucans and endotoxin modifies the risk of allergic diseases at 10 years of age.

METHODS

The concentrations of mite, cat and dog allergens, endotoxin and beta(1,3)-glucans were determined in dust from the homes of 260 two-year-old children with lung function measured at birth (tidal flow volume loops) in the Environment and Childhood Asthma study in Oslo. At 10 years, the health status was assessed in a follow-up study including a structured interview of the parents and an extended clinical examination.

RESULTS

Cat and dog keeping at 2 years of age was reported in 6.5% and 5.5% of the families, respectively. Mite allergens were detected in only 4/260 dust samples. The adjusted odds ratio for asthma at age 10 was 1.20 (95% confidence interval: 1.01-1.43) and 1.22 (1.02-1.46) for bronchial hyperresponsiveness (BHR) per 10 microg/g dust increase in cat allergen exposure at 2 years of age. No association was seen with allergic sensitization. Moreover, endotoxin and beta(1,3)-glucan exposure did not modify the risk of asthma or allergic sensitization. None of the measured environmental factors were associated with lung function at 10 years of age or a relative change in lung function from birth.

CONCLUSION

In a community with a low prevalence of pet keeping and low mite allergen levels, exposure to cat allergens early in life increased the risk of late childhood asthma and BHR, but not the risk of allergic sensitization. No risk modification was seen for dog allergens, endotoxin and beta(1,3)-glucans.

Do allergic families avoid keeping furry pets?

Studies addressing the relationship between pet keeping and development of asthma and allergies may be influenced by pet avoidance in families with a history of allergic disease. Following a cohort of 1019 children in Oslo till 10 years of age, we studied the association of pet keeping with socio-economic factors and allergic disease in the family. A family history of asthma and rhinoconjunctivitis was not significantly associated with pet ownership at birth or with pet removal by 10 years. Acquiring cats and dogs was less likely if the child had allergic rhinoconjunctivitis, whereas no association was seen with asthma (in any family member). Single parenthood increased the likelihood of acquiring a cat, smoking parents more often had cats or dogs, and having older siblings was associated with keeping dogs and other furry pets. Among 319 families reporting pet avoidance, 70% never had pets, 8% had given up pets, and 22% avoided a particular type of pet only. Twenty-four per cent of the parents failed to retrospectively report pet keeping during the child's first year of life. Overall, allergic rhinitis, but not asthma was associated with actual pet avoidance, whereas the strongest predictors for keeping pets were found to be socio-economic factors.

PRACTICAL IMPLICATIONS

Allergic disease in a child most often does not lead to the removal of the family's furry pet. Pet avoidance is associated with allergic symptoms, but not asthma. Socio-economic factors like parental education, single parenthood and smoking affects the families' decisions on pet keeping, including the type of pets the families will avoid or acquire. The large recall error demonstrated points to the need for prospective data regarding pet keeping.

Contact to cat or dog, allergies and parental education

Whether or not associations between animal contact and allergy/atopy are homogeneous across social strata has not yet been investigated. The aim of this study was to estimate the association between animal contact (cat, dog) and allergy/atopy in 6-yr-old school beginners, stratified by parental educational level. A total of 30794, 6-yr old children participated in cross-sectional studies between 1991 and 2000 in Germany. Allergic sensitization to common aeroallergens and symptoms and diagnoses of atopic diseases (asthma, eczema, hay fever) were the dependent variables. Contact with dog/cat were the independent variables. Logistic regression was used to adjust for confounding. Analyses were stratified for parental education. Prevalences of hay fever, eczema, specific sensitization to pollen and house dust mite increased, while the prevalence of contact to cat and dog decreased with parental educational level. Globally significant positive associations between cat contact and sensitization to cat (interaction significant) and between dog contact and wheezing remained significant in the highest and medium/highest educational strata respectively. A globally significant inverse association between cat contact and hay fever remained significant in the highest educational stratum only. The inverse association of contact to dog with eczema was globally significant, but not in the strata. When estimating the associations between animal contact and allergy/atopy in children, effect modification by social status should be considered. Cat contact seems to increase the odds of sensitization to cat only in children whose parents have a high level of education.

Effects of pet exposure in the first year of life on respiratory and allergic symptoms in 7-yr-old children. The SIDRIA-2 study

The effects of pet exposure on the development of respiratory symptoms have recently been the matter of vivid discussion. Our objective was to determine the effects of exposure to cat or dog in the first year of life on subsequent respiratory/allergic symptoms in children in a large Italian multicentre study. As part of the SIDRIA-2 Study (Studi Italiani sui Disturbi Respiratori dell'Infanzia e l'Ambiente 2002), the parents of 20016 children (median age 7 yr) provided information on indoor exposures at different times in life and respiratory/allergic symptoms through questionnaires. Logistic regression analyses were performed taking into account cat or dog exposure at different times in life and adjusting for the presence of the other pet, mould exposure, gender, age, parental education, maternal smoking during the first year of life, current passive smoking, family history of asthma/rhinitis/eczema and other potential confounders. Neither significant effects of dog exposure in the first year of life nor in other periods were found on respiratory/allergic symptoms after adjusting for the other covariates. Cat exposure in the first year of life was significantly and independently associated with current wheezing [OR (95% CI) 1.88 (1.33-2.68), p < 0.001] and current asthma [1.74 (1.10-2.78), p < 0.05] and border-line associated with current rhinoconjunctivitis [1.43 (0.97-2.11), p = 0.07]. No other effects of cat exposure were found on respiratory/allergic symptoms. Cat, but not dog, exposure in the first year of life is an independent risk factor for current wheezing, current asthma and current rhinoconjunctivitis at the age of 7.

Prevalence and factors linked to atopy in 10-and 11-year-old children in Almería, Spain

BACKGROUND

During the last decades there has been an increase in both allergic diseases and allergic sensitisation, probably due to changes in the environment and living habits. ISAAC Phase II was designed to establish the prevalence and associated factors to asthma and allergic disorders in childhood.

AIM

To assess the prevalence and factors linked to atopy in 10-11 year-old children from Almería (Spain).

METHODS

As a part of ISAAC II, a survey was conducted among a sample of 1143 schoolchildren using standardised questionnaires and skin-prick testing.

RESULTS

The overall prevalence of atopy was 42.5%. Most common sensitisations were to Dermatophagoides pteronyssinus (36.2%), D. farinae (32.3%), cat (10.8%), Alternaria (7%), grass (6%), and tree pollen (1.7%). 34.9% of these sensitisations could be regarded as subclinical sensitisations. The fractions of asthma, rhinitis and eczema attributable to atopy were 49.2%, 40.4% y 18.6%, respectively. After multivariate analysis, the risk of atopy was significantly lower among females (OR 0.62, CI 95% 0.45-0.86); children with older siblings (OR 0.67; CI 95% 0.49-0.92); intestinal parasites (OR 0.68; CI 95% 0.48-0.97); contact with farm animals in the past (OR 0.48 CI 95% 0.23-0.99); or other animals at present (OR 0.53 CI 95% 0.30-0.95). To have an allergic father (OR 2.96 CI 95% 1.77-4.94) was the only significant risk factor.

CONCLUSIONS

We found several independent factors which significantly protect against atopic sensitisation. These protective factors were not the same for asthma, rhinitis or eczema, suggesting that other factors could interact to influence atopy and act against such protective factors.

Cats and dogs and the risk of atopy in childhood and adulthood

BACKGROUND

Exposure to cats and dogs during childhood has been linked to a lower risk of developing allergies. It remains unclear whether this is due to selective avoidance of pets by families with a history of allergies. The effects of pet ownership in adulthood are unknown.

OBJECTIVES

We sought to assess the association between cat and dog ownership in childhood and early adulthood and the development of atopy in a population-based birth cohort of 1037 subjects.

METHODS

Ownership of cats or dogs between birth and age 9 years and between the ages of 18 and 32 years was reported. Skin prick tests to common allergens were performed at 13 and 32 years.

RESULTS

There was no evidence that families with a history of atopy avoided owning pets. There were significant cat-by-dog interactions for the development of atopy in both childhood and adulthood. Children who had owned both a cat and a dog were less likely to be atopic at age 13 years. Living with only one of these animals was not protective against atopy. Among those who were not atopic by age 13 years, having both a cat and a dog in adulthood was associated with a lower risk of new atopy by age 32 years. This association was only significant among those with a parental history of atopy. These effects were independent of a range of potential confounding factors.

CONCLUSIONS

There is a synergistic interaction between cat and dog exposure that is associated with a lower risk of developing atopy in childhood and young adulthood.

Effects of pets on asthma development up to 8 years of age: the PIAMA study

BACKGROUND

Recall bias may provide discrepant relationships of pet exposure with sensitization and asthma development. We studied prospectively effects of pets at home on development of sensitization, asthma and respiratory symptoms from birth up to age 8 years.

METHODS

Event history analysis was performed on annually registered data of 2951 children, participating in the PIAMA birth cohort study.

RESULTS

Children with a cat or dog at home at 3 months of age had a significantly lower prevalence of sensitization to inhalant allergens at age 8, but not of asthma. A cat decreased the risk of house dust mite sensitization at age 8 [odds ratio (OR) = 0.68, 95% confidence interval (CI) 0.49-0.95], a dog of pollen sensitization (OR = 0.49, 95% CI: 0.29-0.83). A cat or dog at home did not significantly affect asthma incidence in each subsequent year. From 2 years of age onwards, the incidence of wheeze (OR = 1.52, 95% CI: 1.12-2.05) and a dry cough at night (OR = 1.28, 95% CI: 1.05-1.57) was higher in children with a dog, whereas removal of a dog increased the risk of developing asthma symptoms. Comparing analyses using prospectively and retrospectively collected data on diagnosed asthma showed important recall bias.

CONCLUSIONS

Our prospective study shows a protective effect of early presence of pets at home on sensitization to inhalant allergens, but no prevention of asthma development. Furthermore, children with pets had more frequent transient or intermittent asthma symptoms. Parental report of asthma by recall may provide spurious results of these associations.

Pets keeping in home, parental atopy, asthma, and asthma-related symptoms in 12,910 elementary school children from northeast China

The effects of pet exposure and parental atopy on respiratory symptoms were investigated in 12,910 children residing in twelve districts of northeast China. Responses to a self-administered questionnaire completed by parents of children were used to ascertain children with persistent cough, persistent phlegm, doctor-diagnosed asthma, current asthma and current wheeze. Exposure to animals during pregnancy was positively associated with doctor-diagnosed asthma [adjusted odds ratio (ORs), 1.86; 95% confidence interval (CI) 1.35-2.57], current asthma (adjusted OR, 3.06; 95% CI, 1.95-4.81) and asthma-related symptoms. Pet exposure in the first year of life and currently having animals in household were also related to a significantly higher prevalence of doctor-diagnosed asthma and asthma-related symptoms in these children. Associations with respiratory symptoms strengthened with higher levels of animal exposure. Parental atopy increased the risk of asthma diagnosis (OR, 3.49; 95%CI, 2.84-4.30), current asthma (OR, 3.94; 95%CI, 2.81-5.54) and asthma-related symptoms. There was an interaction between parental atopy and pet exposure in persistent phlegm, but not in doctor-diagnosed asthma. We conclude that pet keeping and parental atopy increased the risk of respiratory symptoms in children. Parental atopy did modify the effect of pet exposure on persistent phlegm but not on doctor-diagnosed asthma.

PRACTICAL IMPLICATIONS

The relationship between exposure to animals and allergic respiratory diseases in childhood is controversial. Inconsistent with other cross-sectional studies mostly conducted in industrialized countries, our study indicates that exposure to animals may increase the occurrence of respiratory symptoms and diseases in children, and the associations with respiratory symptoms strengthened with higher levels of animal exposure parental atopy did modify the effect of pet exposure on persistent phlegm but not on doctor-diagnosed asthma. These findings support the view that measures should be taken to reduce animal exposure for children in China.

Early Interventions in Allergic Diseases

Atopy has been defined as the genetic predisposition to develop IgE antibody responses to a variety of common environmental allergens. Clinically, atopy is expressed by asthma, allergic rhinoconjunctivitis and atopic dermatitis. It has been recognized that the “atopic march” evolves from food allergy and atopic dermatitis in the first 2 years of life, followed by asthma and allergic rhinitis. Over the past 30 years, the prevalence of allergies and asthma has increased significantly in developed countries, and asthma is one of the most common chronic diseases in children. Evidence indicates that environmental factors acting early in life, including respiratory viral infections, exposure to pets and microbial products, day-care attendance, breast feeding, and exposure to allergens, tobacco smoke and other pollutants, are key events for establishment of sensitization and development of chronic, persistent symptoms of allergic diseases [1]. It is thought that gene—environment interactions play a crucial role in these processes. Therefore, attempts to successfully prevent development of allergic diseases should be a priority.

At present, there are no genetic markers for atopy or asthma which could be used routinely in clinical practice and family history of atopy has been used to identify children genetically at-risk of developing allergic diseases. These children from high-risk families have been the focus of most of the intervention studies.

Early exposure and sensitization to cat and dog: different effects on asthma risk after wheezing in infancy

Birth cohort studies have suggested that early exposure to furred pets protects from later asthma and allergy. The aim of the present study was to evaluate the association between exposure or sensitization to cat or dog in infancy, and later asthma and allergy assessed at the median ages of 4.0, 7.2 and 12.3 yr, in children who have wheezed at <24 months of age. Exposure to cat and dog in infancy was assessed by interviewing the parents. The child was considered as sensitized, if the allergen-specific IgE to cat or to dog was >or=0.35 kU/l, or if there was a positive skin test response. When the 20 children with persistent childhood asthma (doctor-diagnosed asthma at all three control visits) were compared with the other 61 children, an early exposure to dog (OR = 0.14, p = 0.034)) decreased the asthma risk and an early sensitization to cat (OR = 5.92, p = 0.008) and dog (OR = 9.33, p = 0.001) increased the asthma risk. There were less cat and dog keeping in atopic families and the effect of sensitization was, but the effect of exposure was not, robust to adjustments in multivariate analyses. The present study demonstrates, in a long-term follow-up after early wheezing, that early sensitization to cat and dog increases the risk of later asthma but early exposure to cat or dog has no such effect. Dog keeping was less frequent in atopic families, which may explain that the protective effect of early exposure to dog was lost in multivariate analyses.

The association of pet keeping at home with symptoms in airways, nose and skin among Bulgarian children

The role of pet exposure in early childhood for allergy/ asthma later in life is still controversial. Recently it was shown that 'avoidance behaviour' is an important factor for the pet distribution in the population. The aim of the present work is to study the association between self-reported pet keeping at home and symptoms in airways, nose and skin among children 2-7 years of age, in a country where primary prevention strategies regarding allergies are not common. A cross-sectional survey on the association between allergy and asthma symptoms and home environmental factors was conducted in two towns in Bulgaria in spring 2004 (the ALLHOME-1 study). Data for 4479 out of 12982 children was obtained. 21.3% of the parents reported having pets at the time of the questionnaire, and 23.3% for pet keeping at index child's birth. Parents of 3.3% of the children got rid of some of the pets and 10.6% refrained from having pets, due in both cases to allergic illness in the family. Keeping dogs or cats at the time of the survey or during the child's first years was associated with most of the symptoms (aOR 1.1-2.2).

Early environmental determinants of asthma risk in a high-risk birth cohort

Environmental exposures during early life have been suggested to have the greatest impact on childhood asthma. Our aim was to evaluate the risk factors associated with asthma at age 7 yr in a high-risk cohort that participated in a randomized controlled study on the primary prevention of asthma. Indoor exposures were characterized before birth and at 2 weeks, 4, 8, 12, 18, and 24 months after birth and again at 7 yr. Nasal scrapings for respiratory viruses were done at the same intervals during the first 2 yr. At age 7, the children were assessed by a pediatric allergist and had allergy skin tests. Logistic regression analysis was undertaken to evaluate the effect of exposures on asthma for the entire cohort with adjustment for group allocation. In addition to the lower risk of asthma in the intervention group, we found a higher prevalence of asthma at age 7 for males, those having a positive history of asthma in mother, father, or older siblings, for children residing in Winnipeg and for atopic subjects. Upon adjustment for intervention group assignment and baseline factors, significant environmental risk factors during year 1 included dog ownership and respiratory syncytial viral infection detected at 12 months while maternal smoking was protective. Dog ownership was a significant risk factor in year 2, but highly correlated with dog ownership in year 1. Indoor environmental exposures during year 7 were not associated with asthma at age 7. Maternal smoking at year 7 was associated with a reduced risk of asthma at 7 yr. Early-life exposures were more important determinants than those in later years. A 'window of opportunity' exists for intervention measures to be applied.

Characterization of the duration from onset of asthma symptoms to asthma disease

BACKGROUND

Little is known about factors associated with progression of childhood asthma from onset of symptoms to index date determined by medical records.

OBJECTIVE

To determine the duration between the onset of asthma symptoms to index date of asthma (ie, time when one met the criteria for asthma) and associated factors.

METHODS

Study participants came from a sample of 839 healthy children, aged 5 to 12 years, who had participated in a previous study. Comprehensive medical record reviews were conducted to determine first documentation of asthma symptoms and index date of asthma. Factors were evaluated for an association with the duration from onset of asthma symptoms to index date of asthma.

RESULTS

Of the study sample, 222 children met the criteria for asthma and had an available onset date of asthma symptoms. The median ages at onset of asthma symptoms and the index date were 5.6 and 7.6 years, respectively. The median duration between onset of asthma symptoms and index date was 2.9 months, and the mean was 17.2 months. There was a tendency for patients with a pet at home (P = .047), exercise-induced symptoms (P = .04), younger age at symptom onset (P = .05), and more severe asthma (P = .05) to have a shorter duration from onset of symptoms to index date.

CONCLUSIONS

The duration from onset of asthma symptoms to index date of asthma varies significantly depending on host and environmental factors. It does not necessarily correlate with commonly recognized risk factors for incidence or severity of asthma.

Risk factors of childhood asthma in Sao Jose do Rio Preto, Sao Paulo, Brazil

BACKGROUND

Epidemiological studies have shown increased prevalence of asthma over the last decades and a considerable variation in these rates between different countries, mainly developed. Changes in lifestyle of different populations could explain the increasing prevalence of asthma and its different rates in different communities.

OBJECTIVES

A case-control study was conducted to investigate some risks factors associated to asthma in schoolchildren in São José do Rio Preto, São Paulo, Brazil.

CASUISTIC AND METHODS

A total of 3793 self-administered written questionnaire (WQ) was filled in by parents of 6-7-year-old schoolchildren, applying the International Study of Asthma and Allergies in Childhood (ISAAC) protocol. Additionally, was added a supplementary WQ evaluating risk factors: gender, personal history of rhinitis and atopic eczema, familial history of atopy, older siblings, day care, breastfeeding, and exposure to pets and to cigarette smoking. Children whose parents responded affirmatively to question 'Has your child had wheezing in the past 12 monthsquest;' were identified as having current asthma.

RESULTS

The prevalence of current asthma was 18.3%. In multivariate analysis the following risk factors were associated with asthma: rhinitis (OR = 10.6; 95% CI = 8.27-13.56), atopic eczema (OR = 1.54; 95% CI = 1.00-2.35), father with asthma (OR = 3.49; 95% CI = 1.83-6.67), mother with asthma (OR = 1.84; 95% CI = 1.11-3.05), current exposure to pets (OR = 1.83; 95% CI = 1.45-2.32) and passive tobacco smoking exposure (OR = 1.43; 95% CI = 1.12-1.83).

CONCLUSIONS

Our results show that genetic background, environmental factors and the presence of co-morbidities such as rhinitis and atopic eczema are associated to the genesis of asthma in Brazilian schoolchildren.

Exposure to furry pets and the risk of asthma and allergic rhinitis: a meta-analysis

BACKGROUND

Exposure to pets has been implicated as a risk factor for asthma. However, this relation has been difficult to assess in individual studies because of the large potential of selection bias. We sought to examine the association between exposure to furry pets and asthma and allergic rhinitis by means of a meta-analysis.

METHODS

We retrieved studies published in any language by searching systematically Medline (1966-March 2007), Embase, LILACS and ISI Proceedings computerized databases, and by examining manually the references of the original articles and reviews retrieved. We included cohort and case-control studies reporting relative risk estimates and confidence intervals of exposure to cats, dogs and unspecified furry animals and subsequent asthma and allergic rhinitis. We excluded cross-sectional studies and those studies that did not measure exposure but rather sensitization to pets.

RESULTS

Thirty-two studies were included. For asthma, the pooled relative risk related to dog exposure was 1.14 (95% CI 1.01-1.29), that related to exposure to any furry pet was 1.39 (95% CI 1.00-1.95). Among cohort studies, exposure to cats yielded a relative risk of 0.72 (95% CI 0.55-0.93). For rhinitis, the pooled relative risk of exposure to any furry pet was 0.79 (95% CI 0.68-0.93).

CONCLUSIONS

Exposure to cats exerts a slight preventive effect on asthma, an effect that is more pronounced in cohort studies. On the contrary, exposure to dogs increases slightly the risk of asthma. Exposure to furry pets of undermined type is not conclusive. More studies with exact measurement of exposure are needed to elucidate the role of pet exposures in atopic diseases.

Exposure to animals and the risk of allergic asthma: a population-based cross-sectional study in Finnish and Russian children

BACKGROUND

There is little information on potential differences in animal exposure between Finland and Russia and particularly on the effects of animal exposure on asthma among Russian children. The aim of the study was to compare the pet and farm animal exposures and to assess the relations of pre- and postnatal animal exposures to the occurrence of allergic asthma in Finnish and Russian school children.

METHODS

We conducted a population-based cross-sectional study in neighbour towns on either side of the Finnish-Russian border; Imatra in Finland and Svetogorsk in Russia. The study population consisted of 512 Finnish and 581 Russian school children aged 7-16 years (response rate 79%). Multivariate logistic regression analysis was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) related to each exposure.

RESULTS

Current indoor exposure to pets was more frequent among school children in Svetogorsk than in Imatra (67.5% vs. 56.0%, P < 0.001). Finnish children were exposed more frequently to dogs, whereas Russian children to cats during childhood and to farm animals during pregnancy and infancy. The risk of self-reported allergic asthma was inversely related to indoor dog keeping ever in Finland (adjusted OR 0.35, 95% CI 0.13, 0.95), whereas in Russia the risk of allergic asthma was increased in relation to combined indoor cat exposure during infancy and currently (4.56, 1.10, 18.91). The risk of asthma was elevated in relation to contact to farm animals during pregnancy (Finland: 1.95, 0.69, 5.50; Russia: 1.90, 0.70, 5.17) and early life (Finland: 2.05, 0.78, 5.40; Russia: 1.21, 0.39, 3.73).

CONCLUSION

Exposure to pets and farm animals during childhood differed significantly between Finland and Russia. Our study provides evidence that early-life exposure to cats increases the risk of asthma whereas exposure to dogs is protective. Our findings suggest that intermittent fetal and early-life exposure to farm animals increases the risk of allergic asthma in urban children visiting farms.

Validity of the interview on pets kept at home for predicting the actual domestic expsoure to their specific allergens. Krakow inner city area study

The aim of the study was to describe the exposure to dog (Can f 1) and cat (Fel d 1) allergens within homes of very young children living with and without pets, and to assess the validity of the interview on pets for predicting the actual exposure to pet allergens in house dust. House dust samples were collected in 275 dwellings from the mattresses, children’s bedroom and kitchen floors. In the laboratory, dust samples were analyzed for Can f 1 and Fel d 1 using monoclonal antibody enzyme-linked immunosorbent assays (ELISA). The majority of households (79.3%) had neither a dog nor a cat living in the home over the past 6 months preceding the survey. Dog allergen above 2 μg/g dust were found in 22.5% of homes and 14.2% of homes contained dog allergen above 10 μg/g of house dust. In the total study sample, cat allergen above 1 μg/g of dust were found in 12.7% of homes, and 3.3% of homes contained Fel d 1 levels greater than 8 μg/g of dust. The majority of children (75.0%) with reported ownership of dogs were exposed to Can f 1 levels above 2 μg/g of house dust, and 73.1% of children with cats at home were exposed to Fel d 1 concentrations above 1 μg/g house dust. The results of the study showed that post-test probability of the true exposure to Can f 1 above 2 μg/g dust in houses with positive interview on indoor dogs was 75.0% (95%CI: 61.7–84.8%). On the other hand, the prediction of exposure estimated from the interview data on indoor dogs produced 12.6% of false negatives (95% CI: 9.9–15.8%). Similarly, the post-test probability of the true exposure to Fel d 1 above 1 μg/g dust in houses with positive interview on indoor cats was 73.1% (95%CI: 55.1–85.7%). On the other hand, the interview data produced 6.4% false negatives (95% CI: 4.6–9.0%). In conclusion, the study demonstrated that homes in Poland with pet ownership are important reservoir of Can f 1 and Fel d 1 allergens with levels that might induce allergic symptoms. Even in homes of children without a dog or cat indoors, there was a higher prevalence of pet allergens at the levels above allergic sensitisation thresholds. This may have an important implication for epidemiologic studies on pet related allergy and prevention practice.

Risk of wheezing associated with house-dust mite allergens and indoor air quality among three-year-old children. Kraków inner city study

OBJECTIVES

The aim of the study was to describe the distribution of house-dust mite (HDM) allergens in homes of three-year-old children and to test the hypothesis whether the content of HDM allergens exceeding 2 microg/g of dust may be regarded as a risk level possibly affecting respiratory health in early childhood.

MATERIALS AND METHODS

House-dust samples were collected in 275 dwellings from mattresses, children's bedrooms and kitchen floors. In the laboratory, dust samples were analyzed for Der f 1 and Der p 1 using monoclonal antibody enzyme-linked immunosorbent assays (ELISA). At the time of the house-dust collection, mothers were interviewed on the household characteristics and their children's respiratory health. Respiratory outcome variables included wheezing or whistling in the chest irrespective of respiratory infections. The number of the wheezing episodes and their duration in days over the last 6 months were recorded in the questionnaire. In the multivariate Poisson regression analysis on the association between the occurrence of wheezing and exposure, a set of potential confounders, such as child's gender, maternal education, maternal allergy, older siblings, presence of moulds, house dampness, and environmental tobacco smoke (ETS) was taken into account.

RESULTS

The adjusted incidence rate ratios (IRR) of wheezing ascribed to a higher HDM level (> 2.0 microg/g dust) were 1.84 (95% CI: 1.45-2.34) for duration of wheezing and 1.56 (95% CI: 0.88-2.75) for episodes. Of the confounders taken into consideration, the presence of moulds had the strongest impact on the risk of wheezing (IRR = 4.24; 95% CI: 3.08-5.84).

CONCLUSION

The data support the view that exposure to a higher level of HDM allergens increases the burden of respiratory diseases in the early childhood and the effect is independent of maternal atopy, ETS, and moulds in homes.

Early exposure to pets: good or bad?

Although pet exposure is known to trigger or worsen allergy symptoms and asthma in patients sensitized to pets, data from recent years has shown that pet exposure in early childhood may actually prevent the development of allergic sensitization and allergic diseases including allergic rhinitis, asthma, and atopic dermatitis. The concept of a protective pet effect remains controversial because these findings have not been duplicated in all studies. Moreover, some studies suggest that pet exposure promotes allergic disease. The protective pet effect may be influenced by multiple factors including type of pet; timing, duration, and intensity of exposure; and genetic factors. The mechanisms behind the protective pet effect remain under investigation but may include alterations in immune development, pet-specific tolerance, and exposure to innate immune stimuli.

Prevention of asthma in childhood

PURPOSE OF REVIEW

The prevalence of asthma is increasing in many parts of the world, particularly in developed countries. The present review focuses on recent literature regarding asthma prevention in childhood.

RECENT FINDINGS

Several environmental exposures in infancy or early childhood are associated with reduced prevalence of asthma, but the mechanisms leading to these associations remain unknown. Recent studies have demonstrated limited success in the prevention of asthma or asthma symptoms with the use of asthma medications, once the therapy is discontinued. Immunotherapy offers another strategy for asthma prevention, and groups treated with this intervention have demonstrated reduced atopy and asthma. Several multi-interventional trials have demonstrated a reduced asthma symptom burden but have not demonstrated significant differences in objective measures such as lung function or bronchial hyper-responsiveness between intervention groups.

SUMMARY

The most promising asthma prevention strategies to date have been those that use a multi-interventional approach employing both dietary and environmental manipulations. More research is needed to assess the long-term follow-up of multi-interventional trials and to evaluate novel intervention strategies in the primary or secondary prevention of asthma in childhood.

Perinatal risk factors for sensitization, atopic dermatitis and wheezing during the first year of life (PIPO study)

OBJECTIVE

To evaluate the influence of perinatal environmental factors on early sensitization, atopic dermatitis and wheezing during the first year.

METHODS

Information on pregnancy-related factors, parental atopic history, environmental factors and the clinical course of the infant until age one was gathered by questionnaires, as part of a prospective birth cohort study (Prospective study on the Influence of Perinatal factors on the Occurrence of asthma and allergies [PIPO-study]). Quantification of total and specific IgE was performed in 810 children and their parents.

RESULTS

Early sensitization was found in 107/810 (13%) of the infants. Multiple regression analysis showed that specific IgE in fathers was a risk factor for early sensitization in their daughters (adjusted odds ratios (OR(adj)) 2.21 (95% confidence interval (CI) 1.10-4.49); P=0.03), whereas in boys, day care attendance was shown to be protective for early sensitization (OR(adj) 0.38 (95% CI 0.20-0.71); P=0.001). Atopic dermatitis occurred in 195/792 infants (25%). Specific IgE in the mother (OR(adj) 1.52 (95% CI 1.06-2.19); P=0.02) and in the infant (OR(adj) 4.20 (95% CI 2.63-6.68); P<0.001) were both risk factors for the occurence of atopic dermatitis, whereas postnatal exposure to cats was negatively associated with atopic dermatitis (OR(adj) 0.68 (0.47-0.97); P=0.03). Postnatal exposure to cigarette smoke (OR(adj) 3.31 (95% CI 1.79-6.09); P<0.001) and day care attendance (OR(adj) 1.96 (95% CI 1.18-3.23); P=0.009) were significantly associated with early wheezing, which occurred in 25% (197/795) of the infants.

CONCLUSION

The effect of paternal sensitization and day care attendance on sensitization is gender dependent. Maternal sensitization predisposes for atopic dermatitis, whereas postnatal exposure to cats had a protective effect.

Primary prevention of childhood asthma and allergic disorders

PURPOSE OF REVIEW

The prevalence of asthma and allergic disorders in childhood is increasing in many parts of the world. This review focuses on recent findings with regard to environmental risk factors and their manipulation in the primary prevention of these diseases in childhood.

RECENT FINDINGS

Recent studies have failed to resolve the controversy on the subject of exposure to indoor aeroallergens and the risk of sensitization and asthma in childhood. Bronchiolitis due to respiratory syncytial virus in infancy is associated with a significant increase in risk of asthma, but not atopy. In the prevention of these diseases, the effects of breastfeeding are controversial, with studies showing a protective effect in children without allergic predisposition, but other studies showing no effect or even the potential for an increased asthma risk. A significant reduction in the prevalence of doctor-diagnosed asthma at 7 years was found in a randomized controlled multifaceted (reduction of inhaled and ingested allergens) intervention study of high-risk infants. Other intervention measures, such as an education program on how to reduce exposure, the use of probiotics, and immunization against infections, all showed some protective effects.

SUMMARY

More research is required, especially with regard to longer periods of follow-up for all current intervention studies aimed at reducing exposure, the onset and duration of intervention, and other novel intervention measures in the primary prevention of asthma and allergic diseases in childhood.

[Epidemiological studies in the HTA evaluation process]

Results of epidemiological studies should be considered as part of the available evidence when evaluating drug treatment benefits in health technology assessment (HTA). Pharmaco-epidemiological databases can provide a broader understanding of the effectiveness of drugs in populations that are frequently underrepresented in clinical trials. Such databases are also useful to investigate drug safety with regard to socio-demographic and medical care-related indicators and hereby contribute to an optimal and targeted pharmacological therapy. Using examples from pharmaco-epidemiological asthma studies, the present article discusses associated difficulties in interpreting database results against the background of various sources of bias and proposes possibilities for integrating observational data into the HTA evaluation process. Researchers are challenged to engage in considerable efforts to develop a standardized inventory of epidemiological methods, e.g. for the pooled analysis of epidemiological data.

2003 canadian asthma consensus guidelines executive summary

BACKGROUND

Guidelines for the diagnosis and management of asthma have been published over the last 15 years; however, there has been little focus on issues relating to asthma in childhood. Since the last revision of the 1999 Canadian Asthma Consensus Report, important new studies, particularly in children, have highlighted the need to incorporate new information into the asthma guidelines. The objectives of this article are to review the literature on asthma published between January 2000 and June 2003 and to evaluate the influence of new evidence on the recommendations made in the 1999 Canadian Asthma Consensus Report and its 2001 update, with a major focus on pediatric issues.

METHODS

The diagnosis of asthma in young children and prevention strategies, pharmacotherapy, inhalation devices, immunotherapy, and asthma education were selected for review by small expert resource groups. The reviews were discussed in June 2003 at a meeting under the auspices of the Canadian Network For Asthma Care and the Canadian Thoracic Society. Data published through December 2004 were subsequently reviewed by the individual expert resource groups.

RESULTS

This report evaluates early-life prevention strategies and focuses on treatment of asthma in children, emphasizing the importance of early diagnosis and preventive therapy, the benefits of additional therapy, and the essential role of asthma education.

CONCLUSION

We generally support previous recommendations and focus on new issues, particularly those relevant to children and their families. This document is a guide for asthma management based on the best available published data and the opinion of health care professionals, including asthma experts and educators.

Greater risk of incident asthma cases in adults with allergic rhinitis and effect of allergen immunotherapy: a retrospective cohort study

Asthma and rhinitis are often co-morbid conditions. As rhinitis often precedes asthma it is possible that effective treatment of allergic rhinitis may reduce asthma progression.

The aim of our study is to investigate history of allergic rhinitis as a risk factor for asthma and the potential effect of allergen immunotherapy in attenuating the incidence of asthma.

Hospital-referred non-asthmatic adults, aged 18–40 years between 1990 and 1991, were retrospectively followed up until January and April 2000. At the end of follow up, available subjects were clinically examined for asthma diagnosis and history of allergen specific immunotherapy, second-hand smoking and the presence of pets in the household. A total of 436 non-asthmatic adults (332 subjects with allergic rhinitis and 104 with no allergic rhinitis nor history of atopy) were available for final analyses.

The highest OR (odds ratio) associated with a diagnosis of asthma at the end of follow-up was for the diagnosis of allergic rhinitis at baseline (OR, 7.8; 95%CI, 3.1–20.0 in the model containing the covariates of rhinitis diagnosis, sex, second-hand smoke exposure, presence of pets at home, family history of allergic disorders, sensitization to Parietaria judaica; grass pollen; house dust mites; Olea europea: orchard; perennial rye; and cat allergens). Female sex, sensitization to Parietaria judaica and the presence of pets in the home were also significantly predictive of new onset asthma in the same model. Treatment with allergen immunotherapy was significantly and inversely related to the development of new onset asthma (OR, 0.53; 95%CI, 0.32–0.86).

In the present study we found that allergic rhinitis is an important independent risk factor for asthma. Moreover, treatment with allergen immunotherapy lowers the risk of the development of new asthma cases in adults with allergic rhinitis.

Primary prevention of allergy and asthma is possible

Allergic diseases, such as asthma, are the result of complex gene-environment interactions. The focus for prevention of allergic disease has been on environmental control. Environmental exposures begin during the intrauterine period, during which a T-helper-2 immune phenotype is promoted. Food allergy frequently occurs during the first year of life, and avoidance of exposure must begin in early pregnancy and must be complete to be effective. Partial avoidance strategies have not been successful. Current data do not allow us to specifically recommend breastfeeding for the prevention of allergy and allergic diseases, but for other important reasons, breastfeeding (particularly exclusive breastfeeding) should be encouraged for at least the first 4 mo of life. Sensitization to allergens is one of the strongest determinants for subsequent development of asthma. There is a strong relationship between exposure to house dust mites, allergen sensitization, and asthma. However, exposure to pets and animals in a farming environment early in life may actually be protective for the development of allergy and asthma. Specific recommendations relating to these exposures requires additional research, but genetics clearly plays an important role in that process. To date, only a multifaceted intervention program has been successful as a primary prevention strategy for the development of asthma in young children. The specific components of the multifaceted intervention and the duration of protection have not yet been defined. It is increasingly clear that gene-directed environmental manipulation undertaken in a multifaceted manner during a "window of opportunity" is critical in the primary prevention of allergy and allergic diseases like asthma.

Allergen avoidance as primary prevention: con

There has been a dramatic increase in the prevalence of atopic diseases, such as atopic dermatitis, food allergy, allergic rhinitis, and allergic asthma. Because environmental factors such as early allergen exposure to nutritional and inhalant allergens have been suspected as potential environmental factors favoring the development of allergic diseases and asthma, primary prevention studies have begun to investigate the effect on sensitization and wheezing. Designs of the studies are different and, therefore, are not completely comparable. Although no clear primary prevention study is available for pets, mite allergen avoidance during infancy can achieve a reduction of specific sensitization and, in some studies, can also produce a slight effect on respiratory symptoms.

High allergen exposure as a risk factor for asthma and allergic disease

The association between pet ownership in childhood and subsequent asthma and sensitization is very controversial. Intriguing, but contradictory, reports have caused considerable uncertainty in parents who wish to avoid asthma and allergic disease in their children. This article argues that high allergen exposure is a risk factor for asthma and allergic disease. It describes dispersal of pet allergens in society and critically assesses epidemiological studies regarding how early exposure to pet allergens affects subsequent immunoglobulin E-sensitization and allergic diseases. Additionally, this article evaluates the effects of allergen exposure in already sensitized subjects with asthma. Cat and dog allergens are ubiquitous in society and may induce sensitization and allergic symptoms in predisposed individuals, regardless of pet ownership. This, in combination with selection mechanisms for pet ownership in families with a history of allergic diseases, makes it difficult to study associations between early exposure to pets and subsequent allergic disease. Nevertheless, exposure to pet allergens worsens asthma in already sensitized children. Thus, it is clear that clinicians should advise sensitized asthmatics that avoidance of exposure to indoor allergens is an important element in the treatment of allergic disease.

Indoor exposures and respiratory symptoms in a Norwegian community sample

BACKGROUND

Limited data are available on the effect of a poor indoor climate on the respiratory health of adults. No data are available regarding the contribution of indoor exposures to the burden of respiratory symptoms in the population.

METHODS

In 1996-7 a community sample of 3181 adults aged 26-82 years was invited to participate in a survey on indoor climate and respiratory health in Hordaland County, Norway. 2401 subjects agreed to take part. Logistic regression was used to examine the relationship between eight markers of indoor exposure and physician diagnosed asthma and five respiratory symptoms, after adjustment for sex, age, smoking, educational level, smoking habits, pack years, and occupational airborne exposure.

RESULTS

Mould exposure was associated with all the respiratory symptoms; the adjusted odds ratios (OR) varied from 1.6 (95% confidence interval (CI) 1.0 to 2.4) for cough with phlegm to 2.3 (95% CI 1.4 to 3.9) for grade 2 dyspnoea. Keeping a cat or dog in childhood was associated with grade 2 dyspnoea and attacks of dyspnoea, with adjusted ORs of 1.3 (95% CI 1.0 to 1.7) and 1.4 (95% CI 1.1 to 1.8), respectively. Having a fitted carpet in the bedroom was negatively associated with three of the five respiratory symptoms. 3-5% of the frequency of the respiratory symptoms in the study population could be attributed to exposure to visible moulds.

CONCLUSION

Mould exposure is an independent risk factor for several respiratory symptoms in a general population covering a wide age span, but it makes only a small contribution to the respiratory symptom burden in the population at large.

The Australasian Society of Clinical Immunology and Allergy position statement: Summary of allergy prevention in children

A family history of allergy and asthma identifies children at high risk of allergic disease. Dietary restrictions in pregnancy are not recommended. Avoiding inhalant allergens during pregnancy has not been shown to reduce allergic disease, and is not recommended. Breastfeeding should be recommended because of other beneficial effects, but if breast feeding is not possible, a hydrolysed formula is recommended (rather than conventional cow's milk formulas) in high-risk infants only. Maternal dietary restrictions during breastfeeding are not recommended. Soy formulas and other formulas (eg, goat's milk) are not recommended for reducing food allergy risk. Complementary foods (including normal cow's milk formulas) should be delayed until a child is aged at least 4-6 months, but a preventive effect from this measure has only been demonstrated in high-risk infants. There is no evidence that an elimination diet after age 4-6 months has a protective effect, although this needs additional investigation. Further research is needed to determine the relationship between house dust mite exposure at an early age and the development of sensitisation and disease; no recommendation can yet be made about avoidance measures for preventing allergic disease. No recommendations can be made about exposure to pets in early life and the development of allergic disease. If a family already has pets it is not necessary to remove them, unless the child develops evidence of pet allergy (as assessed by an allergy specialist). Women should be advised not to smoke while pregnant, and parents should be advised not to smoke. No recommendations can be made on the use of probiotic supplements (or other microbial agents) for preventing allergic disease at this time. Immunotherapy may be considered as a treatment option for children with allergic rhinitis, and may prevent the subsequent development of asthma.

"Early" cat ownership and the risk of sensitization and allergic rhinitis in Ligurian children with respiratory symptoms

BACKGROUND

Studies on the role of cat ownership in the development of allergy have lead to conflicting results, probably owing to heterogeneity of the populations evaluated.

OBJECTIVE

To evaluate the possible effect of cat ownership on the frequency of sensitization and asthma or rhinitis in children living in Liguria, Italy, who attended a pediatric clinic for respiratory symptoms.

METHODS

We enrolled 269 consecutive school-aged children in 12 months. Sensitization to aeroallergens by skin prick testing and the presence of respiratory symptoms (ie, asthma and rhinitis) were evaluated. To analyze the role of different independent variables in association with respiratory symptoms and sensitization, a multiple logistic regression analysis was performed.

RESULTS

Of 269 children, 81 were exposed to cats at home in the first 2 years of life ("early" cat owners), 65 after the first 2 years of life ("late" cat owners), and 123 never ("never" cat owners). Early cat ownership was significantly associated with a lower risk of cat sensitization compared with never cat ownership (adjusted odds ratio [ORadj], 0.32; 95% confidence interval [CI], 0.14-0.74; P = .01). Early cat ownership was also associated with a significantly lower risk of allergic rhinitis than late cat ownership (ORadj, 0.43; 95% CI, 0.22-0.85) or never cat ownership (ORadj, 0.51; 95% CI, 0.28-0.92). No differences in the frequency of asthma were found among the 3 groups (P = .74)

CONCLUSIONS

Cat ownership in early childhood can play an important role in preventing sensitization to cat and in lowering the frequency of allergic rhinitis, at least in children with the characteristics of the population studied.

The effect of pet ownership on the risk of allergic sensitisation and bronchial asthma

An increasing volume of evidence suggests that early contact of children with the allergens of furred pets (especially those produced by cats) may determine a lower risk of developing allergic sensitisation to these materials. A possible explanation of this data is that an early inhalation of high levels of the major cat allergen Fel d 1 induces the production of IgG and IgG4 antibodies with a "protective" effect. Other authors have shown that the prevalence of allergic sensitisation to cats, in adults, is reduced in those patients exposed to the lowest and highest levels of the allergens. On the contrary, the risk of developing sensitisation to cats is significantly higher when the patients were exposed to intermediate levels of Fel d 1. Moreover, epidemiological studies have demonstrated a relatively low prevalence of cat allergy (about 10%) in some countries where rates of cat ownership are high. This data confirms the role of indirect exposure to pet allergens in inducing allergic sensitisation. Clothes of pet owners have been indicated as the carriers for the dispersal of these allergens in pet-free environments. However, it is important to point out that exposure of highly sensitised patients to relevant amounts of pet allergens (such as in a pet shows/shops) may determine a dramatic exacerbation of nasal and/or bronchial symptoms.

Longitudinal study on the relationship between cat allergen and endotoxin exposure, sensitization, cat-specific IgG and development of asthma in childhood--report of the German Multicentre Allergy Study (MAS 90)

BACKGROUND

Controversial data have emerged regarding the question whether cat exposure in childhood favours or decreases the risk of sensitization and allergic airway disease. In a prospective birth-cohort study, we assessed the association between longitudinal cat allergen exposure, sensitization (immunoglobulin E, IgE), IgG antibody (ab) levels to cat and the development of asthma in children up to the age of 10 years.

METHODS

Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 10 years were available for 750 children. Assessments included yearly measurements of specific serum IgE to cat and at age 6 and 18 months, 3, 4 and 10 years measurement of cat allergen Fel d 1 in house dust samples. Additionally, Fel d 1-specific IgG ab were determined in 378 serum samples of 207 children. Endotoxin exposure in mattress dust was measured in a subgroup of 153 children at age 10 years. From age 4 years on, International Study of Asthma and Allergy in Childhood (ISAAC) questionnaires were completed yearly in order to assess the prevalence of wheeze and asthma.

RESULTS

Serum IgG-levels to cat showed a large variation, however, intraindividually values showed rather constant concentration over a longer time period. The IgG levels at school-age correlated with cat allergen exposure during the first 2 years of life. Specific IgE to cat was clearly associated with wheeze ever, current wheeze and bronchial hyperresponsiveness (BHR), this was also observed for children with specific IgE ab to cat (>0.35 kU/l) plus IgG levels above 125 U/ml. A large percentage of very highly exposed children showed high IgG but no IgE responses to cat, however, not all highly exposed children were found to be protected from sensitization. Children with IgG but without IgE ab to cat showed the lowest prevalence of wheeze ever and current wheeze despite high cat allergen exposure, however, this trend did not achieve significance. While homes of cat owners showed higher Fel d 1 concentrations than homes without cats, homes of cat owners were not found to have higher endotoxin levels in carpet dust samples than homes without cats.

CONCLUSIONS

We could confirm that high cat allergen exposure in a cohort with lower community prevalence of cats is associated with higher serum IgG and IgE levels to cat in schoolchildren. Sensitization to cat allergen (IgE) is a risk factor for childhood asthma. While exposure to cat allergen during infancy is associated with sensitization (IgE), only in the very highly exposed children the likelihood of sensitization (IgE) is decreased and high IgG levels to cat without IgE were associated with low risk of wheeze. However, cat-specific IgG ab levels did not protect children with IgE-mediated sensitization from wheeze.