Does early exposure to cat or dog protect against later allergy development?

[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.

Indoor pet exposure and the outcomes of total IgE and sensitization at age 18 years

BACKGROUND

Early-life exposure to household pets has been shown to be protective against allergic sensitization in childhood.

OBJECTIVE

We sought to evaluate the association between early-life pet exposure and allergic sensitization at age 18 years.

METHODS

Teenagers who had been enrolled in the Detroit Childhood Allergy Study birth cohort in 1987-1989 were contacted at age 18 years. Serum total and allergen-specific IgE levels to 7 common allergens (dust mite, cat, dog, ragweed, Timothy grass, Alternaria species, and peanut; atopy was defined as any specific IgE level > or =0.35 kU/L) were measured at age 18 years. Annual interview data from childhood were used to determine indoor dog and cat (> or =50% of their time in the home) exposure during early life. Exposure was considered in various ways: first year, cumulative lifetime, and age groups, as well as multiple pets.

RESULTS

Dog or cat exposure in the first year of life was not associated with atopy (relative risk, 0.97; 95% CI, 0.83-1.12). Those living with pets in the first year and atopic at 18 years had lower total IgE levels. Neither cumulative exposure nor exposure at a particular age was strongly and consistently associated with either outcome. Although not statistically significant, there was a pattern of decreased odds of sensitization among those with 2 or more pets versus no pets in the first year of life.

CONCLUSIONS

Early-life pet exposure can be associated with lower total IgE levels among atopic subjects but is not strongly associated with decreased likelihood of sensitization to common allergens at age 18 years.

The Obstructive Lung Disease in Northern Sweden (OLIN) longitudinal paediatric study I--the first 10 years

BACKGROUND

Prospective studies of asthma and allergic conditions based on the general population are scarce.

AIM

To summarize the methods and main results from a prospective study among school children.

METHODS

In 1996, a cohort of 3525 children aged 7/8 years in Northern Sweden were invited to a questionnaire survey using an expanded ISAAC protocol, and 97% participated. The cohort has been followed up yearly with high participation rate. Skin prick tests were conducted 1996, 2000 and 2006/2007. Allergens in dust from homes and schools have been analyzed. Sub samples have participated in interviews, lung function tests, bronchial hyper reactivity test, and analyses of IgE and IgG antibodies in serum.

RESULTS

The prevalence of asthma was 6% at age 7-8 years and increased by age. The incidence of physician-diagnosed asthma after the age of 7-8 years was around 1/100/year. The prevalence of positive skin prick test increased from 21% at age 7-8 to 30% at age 11-12 years. Remission of allergic sensitization was rare, while asthma remission was 5% yearly. The main risk factor for asthma and allergic sensitization increased in importance with increasing age. Allergic and non-allergic asthma had different risk factor pattern. Environmental risk factors decreased in impact after the age of 7. Avoidance of pets at home did not protect from asthma or allergic sensitization.

CONCLUSION

The study includes important sources of data for further longitudinal analyses that will contribute to the understanding of the development and the nature of asthma and allergic sensitization.

What has the ECRHS told us about the childhood risks of asthma, allergy and lung function?

Few studies investigate how environmental factors in childhood may influence adult respiratory health. The European Community Respiratory Health Survey (ECRHS) is a longitudinal multi-centre study of Western world adults, including retrospective assessment of early life factors. Analyses of the ECRHS showed both beneficial and harmful long-term effects of childhood factors on adult asthma, allergy and lung function. Childhood pets were associated with less adult atopy and hay fever; beneficial effects were also indicated for growing up on a farm and for early exposure to other children. The findings have contributed to further development of the hygiene hypothesis and further understanding of the mechanisms relating microbial stimulation to allergy; however, the public health consequences may be limited. Harmful effects of early life factors on adult asthma and lung function were indicated for severe respiratory infections early in life, parental smoking and long-term dog keeping. Intervention with regard to parental smoking and vaccination against common lower airways infections may improve respiratory health in the population. Thus, early life environment had permanent beneficial and adverse effects on adult respiratory health. The multi-centre structure of the ECRHS, the large sample size, the extensive information about each participant and follow-up until the age of 56 years, have given the basis for convincing conclusions, and made possible publication of unsuspected findings in spite of the problems related to adult recall of childhood events. The ECRHS have contributed substantially to increased knowledge about the early life origins of allergy and obstructive pulmonary disease, providing a basis for prevention.

Dysregulated Th1 and Th2 responses in food-allergic children--does elimination diet contribute to the dysregulation?

Infants with eczema and sensitization to foods are recommended skin care and, if food allergy is proven, an elimination diet. Although most of these children tolerate foods before 3 yr of age, some children experience prolonged food allergy. To our knowledge, no prospective study has investigated the cytokine profile in food-sensitized eczematous children with prolonged food intolerance. The aim of the study was to prospectively investigate the development of cytokine production induced by food allergen in food-sensitized eczematous children who, at 4(1/2) yr of age, were allergic or tolerant to egg or milk. Twenty-one eczematous infants, [age 5 (3-10) months; median and range], sensitized to egg and/or milk were included, put on elimination diet and followed prospectively. At 4(1/2) yr of age, the children were defined as tolerant or allergic to egg and/or milk based on open or double-blind placebo-controlled food challenges. Peripheral blood mononuclear cells (PBMC) were isolated from the children on inclusion, after 6 wk of elimination diet, and at 3 and 4(1/2) yr of age. Ovalbumin, beta-lactoglobulin and tetanus toxoid-induced IL-4, -5, -10, -13 and IFN-gamma production from PBMC were analyzed with enzyme-linked immunosorbent assay. The IFN-gamma and IL-5 secretion induced by food allergen at 4(1/2) yr was higher in cell cultures from children who were allergic to egg or milk than in tolerant children. In food-allergic children, the levels of IFN-gamma and IL-5 were higher at 4(1/2) yr compared with inclusion levels, but this increase was generally not observed in the tolerant children who consumed milk and egg. In conclusion, immune cells from food-allergic children on an elimination diet respond with up-regulated T helper 1 and T helper 2 cytokine secretion induced by food allergen. We hypothesize that allergen elimination may influence the regulatory mechanisms maintaining balanced immune responses to innocuous food antigens.

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.

Interleukin-4 receptor polymorphisms in asthma and allergy: relation to different disease phenotypes

AIM

Inheritance and genetic factors are supposed to influence susceptibility to asthma and allergy. We tested if single nucleotide polymorphisms (SNPs) in the IL4R gene were associated with susceptibility to such diseases, or if they were related to the phenotypic presentation of asthma and allergic rhinoconjunctivitis (ARC).

METHODS

Three hundred and nine 12- to 13-year-old children were included. Six SNPs in the IL4R were analysed in response to current allergic disease, and to presentation of specific asthma and ARC phenotypes. Questionnaires were used to determine allergic disease status, and skin prick tests to evaluate sensitization to common airborne allergens.

RESULTS

Less eczema was seen in individuals with the AA-genotype of rs2057768, and less ARC among those with the AA-genotype of rs2107356, especially ARC associated with sensitization to pollen. The AA-genotype of rs2057768 and the TT genotype of rs3024632 were associated with a specific asthma phenotype.

CONCLUSION

Variations within the IL4R gene are associated with allergic diseases in children, preferably with eczema and disease phenotypes of ARC and asthma.

Effects of early cat or dog ownership on sensitisation and asthma in a high-risk cohort without disease-related modification of exposure

Variation in the observed association between pet ownership and allergic disease may be attributable to selection bias and confounding. The aim of this study was to suggest a method to assess disease-related modification of exposure and second to examine how cat acquisition or dog ownership in early life affects atopy and asthma at 5 years. Information on sociodemographic factors and cat and dog ownership was collected longitudinally in an initially cat-free Australian birth cohort based on children with a family history of asthma. At age 5 years, 516 children were assessed for wheezing, and 488 for sensitisation. Data showed that by age 5 years, 82 children had acquired a cat. Early manifestations of allergic disease did not foreshadow a reduced rate of subsequent acquisition of a cat. Independent risk factors for acquiring a cat were exposure to tobacco smoke at home odds ratio (OR) 1.92 [95% confidence interval (CI) 1.13, 3.26], maternal education < or =12 years OR 1.95 [1.08, 3.51] and dog ownership OR 2.23 [1.23, 4.05]. Cat or dog exposure in the first 5 years was associated with a decreased risk of any allergen sensitisation, OR 0.50 [0.28, 0.88] but no association with wheeze OR 0.96 [0.57, 1.61]. This risk was not affected by age at which the cat was acquired or whether the pet was kept in- or outdoors. In conclusion, cat or dog ownership reduced the risk of subsequent atopy in this high-risk birth cohort. This cannot be explained by disease-related modification of exposure. Public health recommendations on the effect of cat and dog ownership should be based on birth cohort studies where possible selection bias has been taken into account.

Neonatal tolerance under breastfeeding influence: the presence of allergen and transforming growth factor-beta in breast milk protects the progeny from allergic asthma

Once the umbilical cord has been cut, immunologists have often looked at the neonate as an entity that develops on its own. For years, breast milk was considered mainly as a source of nutrients for the developing child. The extensive observations that breastfeeding affords protection toward infectious diseases and could reduce by more than the half the mortality rate because of common infections have added another key role to breastfeeding. This protection relies in great part on the passive transfer through breast milk of high amounts of microbe-specific immunoglobulins that compensate for the deficiency of immunoglobulins synthesis during the first year of life. Here, we will present and discuss our data showing how breast milk can actively shape the immune response of the progeny, particularly in the context of allergic disease. Indeed, our data obtained in a mouse model suggest that the protection attributed to breastfeeding toward asthma development might rely on immune tolerance induction. For this to occur, the mother mice needed to be exposed to the allergen by aerosol or oral route during the lactation period, which resulted into the transfer of the allergen to breast milk. The presence of the allergen together with transforming growth factor-beta in breast milk was necessary and sufficient to induce the development of regulatory T lymphocytes in the progeny and their protection from asthma development. If confirmed in human beings, this study may suggest new strategies for asthma prevention such as deliberate exposure of mother to allergens during breastfeeding and qualitative modification of artificial milks.

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.

Major increase in allergic sensitization in schoolchildren from 1996 to 2006 in northern Sweden

BACKGROUND

Time trends for allergic sensitization are poorly known.

OBJECTIVE

To compare the trends in prevalence of allergic sensitization and associated risk factors in children.

METHODS

Two cohorts of children (age 7-8 years) were invited for skin prick tests (SPTs) 10 years apart, 1996 and 2006. The participation rates were 2148 (88%) and 1700 (90%), respectively. The methods were identical, and 10 common airborne allergens were used. An expanded International Study of Allergy and Asthma in Children questionnaire about symptoms and possible risk factors for allergic conditions was completed by the parents.

RESULTS

The prevalence of any positive SPT increased from 21% in 1996 to 30% in 2006 (P < .001). The pattern of sensitization remained similar, and sensitization to cat was most common both years, 13% and 19%, respectively. Sensitization to mites and mold was uncommon in both surveys. A family history of allergy was a significant risk factor for a positive SPT both years (odds ratio, 1.7). Factors that in 1996 had a protective effect, such as rural living and having several siblings, had lost this effect in 2006. The prevalence of most risk factors remained similar, but respiratory infections and smoking among parents decreased significantly. During the same period, there was no significant increase in the prevalence of current wheeze (11.9% to 12.4%, P = .636) or symptoms of rhinitis or eczema.

CONCLUSION

The prevalence of allergic sensitization increased significantly from 1996 to 2006, whereas no increase in clinical symptoms was found. The parallel decrease in parental smoking and respiratory infections indicate a different influence of environmental factors on allergic sensitization and clinical symptoms, respectively.

Does eczema lead to asthma?

The nature of the relationship between eczema, asthma, and allergic rhinitis has been controversial. It has been commonly held that these disorders, while sharing genetic and environmental risk factors, are unrelated disorders that may develop sequentially along an atopic pathway. Conversely, the link between eczema and these later-onset respiratory disorders may be causal. This review examines the relationship between eczema, asthma, and allergic rhinitis in the context of the atopic march, the skin barrier, and recent developments in eczema genetics; and we propose that the relationship is causal. We describe a plausible biological pathway with eczema as the first step in a progressive atopic march that over time leads to asthma and/or allergic rhinitis. Such a pathway has implications for our understanding of these disorders and steps that might be made to prevent the development of asthma in particular. We propose that intervention studies in eczema should be conducted to confirm or refute this causal relationship. Such studies may materially improve the quality of life of eczema patients and will have important public health benefits if the interventions lead to a reduction in the burden of asthma.

High levels of grass pollen inside European dairy farms: a role for the allergy-protective effects of environment?

BACKGROUND

There is evidence of an allergy protective effect in children raised on farm. It has been assumed that microbial exposure may confer this protection. However in farm, little attention has been given to the pollen level and to concomitant microbiological exposure, and indoor pollen concentrations have never been precisely quantified.

METHODS

The kinetics of pollen in dairy farms have been studied in a pilot study (n = 9), and exposure in a sub-sample of the ongoing European birth cohort PASTURE (n = 106). Measurements of viable microorganisms and pollen were performed in air samples. To identify factors that modulate the pollen concentration multivariate regression analyses were run.

RESULTS

Indoor pollen (95% of Poaceae fragments and grains) were significantly higher in winter than in summer (P = 0.001) and ranged between 858 to 11 265 counts/m(3) during feeding in winter, thus exceeding typical outdoor levels during the pollen season. Geometric mean in French farms was significantly higher than in German and Swiss farms (7 534, 992 and 1 079 count/m(3), respectively). The presence of a ventilation system and loose housing systems significantly reduced indoor pollen levels. This pollen concentration rise after feeding was accompanied by an increase in fungal and actinomycetal levels, whereas the concentration of bacteria was not associated with feeding.

CONCLUSIONS

Farmers and their children who attend cowsheds during the feeding sessions are exposed perennially to high pollen concentrations. It might be speculated that the combined permanent exposure to microbes from livestock and grass pollen may initiate tolerance in children living on a farm.

Cross-sectional survey of risk factors for asthma in 6-7-year-old children in New Zealand: International Study of Asthma and Allergy in Childhood Phase Three

AIM

To identify risk factors for asthma in primary school-aged children in New Zealand.

METHODS

A cross-sectional survey of 10,873 6-7-year-old children in Auckland, Bay of Plenty, Nelson and Christchurch (a response rate of 85.2%). A questionnaire was completed by the parent or care giver.

RESULTS

22.2% of children wheezed in the last 12 months (current wheeze). Maori children were at greater risk of current wheeze compared with European children (adjusted odds ratio (adjOR) = 1.37; 95% confidence interval = 1.18-1.59). Antibiotics and paracetamol used in the first year of life were associated with an increased risk of current wheeze (adjOR = 1.78 (1.56-2.04) and adjOR = 1.31 (1.06-1.61), respectively). Watching television for 5 or more hours per day was associated with an increased risk of current wheeze (adjOR = 1.44 (1.13-1.83)). Milk and egg consumption in the last 12 months was associated with a reduced risk of current wheeze.

CONCLUSIONS

 This study has identified risk factors for asthma in children aged 6-7 years, although causal pathways cannot be established. These associations have important public health implications if causal.

Cat sensitization according to cat window of exposure in adult asthmatics

BACKGROUND

In adults, there is limited information on tolerance to cat, which may be reflected by high IgG4 without IgE sensitization. Early exposure to cat may play a critical role.

OBJECTIVE

The aim was to assess among adults the association of Fel d 1 IgG4, Fel d 1 IgE, skin prick test (SPT) response to cat and pet-related symptoms in relation to exposure to cat considering the period of exposure.

METHODS

SPT response to cat, specific IgE and IgG4 to Fel d 1 were assessed in 167 asthmatics recruited in chest clinics (40 years of age in average) from the French Epidemiological study on the Genetics and Environment of Asthma (EGEA). Childhood and/or current exposure to cat were studied retrospectively.

RESULTS

IgG4 was higher in relation to current cat exposure (0.53 vs. 0.09 ng/mL; P<0.001) and higher in women than in men. The period of cat exposure was significantly related to Fel d 1 IgE, the IgE/IgG4 pattern and cat weal size. The lowest values of Fel d 1 IgE, cat weal size, pet-related nasal or respiratory symptoms were observed in those with both childhood and current exposure as well as the highest proportion of the IgE-/IgG4+ pattern observed in 1.4%, 4.0%, 38.1% and 12.5% of those with -/-, +/-, +/+, -/+ childhood/current exposure, respectively.

CONCLUSIONS

Adult asthmatics exposed to cats since childhood present an immunologic pattern with high IgG4 and low IgE. Continuous exposure may maintain a state of immunological tolerance to cat.

The role of indoor allergens in the development of asthma

PURPOSE OF REVIEW

Asthma prevalence has markedly increased over the past 30 years. Although atopy and exposure to environmental allergens are known to exacerbate asthma, recent literature supports a causal role of indoor allergens in disease development.

RECENT FINDINGS

High-risk birth cohorts continue to point to atopy as the main risk factor for developing asthma. Exposure to perennial allergens has also been linked to the development of asthma, though with less consistency. Intervention at the level of allergen exposure and allergic immune response is promising.

SUMMARY

The current model of atopic asthma, the predominant phenotype, incorporates genetic and environmental factors in the development of disease. Although genetic factors are less malleable, the environmental component lends itself to analysis and modification.For many, the development of asthma starts with allergen exposure leading to atopic sensitization and subsequent disease. Several studies support the progression from exposure to sensitization with the potential of extremely high levels of exposure leading to tolerance. Likewise, the progression from atopy to asthma is well documented,especially in genetically predisposed children. Recent intervention trials confirm these findings and begin to show promise for the prevention of asthma by interrupting the allergen exposure==>allergen sensitization==>atopic asthma pathway.

Wheezing and Asthma in childhood: an epidemiology approach

Wheezing/asthma in children is a complex problem due to its heterogeneous condition, with different pathogenic mechanisms, variations in duration and in severity; that make it difficult to totally understand. This relation between wheezing in infants and later development of asthma will be the result of alterations in the immune system maturation and congenital or acquired modifications of the airway. Several longitudinal studies have given us important information about the different phenotypes of wheezing/asthma that coexist in children. In this review, we analyse the recent potential mechanisms and risk factors for each of the three classic wheezing phenotypes presenting in children: transient, non-atopic and atopic; and we propose for consideration a fourth phenotype: overweight/obese girls with early menarche. A better understanding of those risk factors would be useful for the development of new strategies in wheezing/asthma management.

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.

Prevalence of asthma among Chinese adolescents living in Canada and in China

BACKGROUND

Studies of the prevalence of asthma among migrating populations may help in identifying environmental risk factors.

METHODS

We analyzed data from Vancouver, Canada, and from Guangzhou, Beijing and Hong Kong, China, collected during phase 3 of the International Study of Asthma and Allergies in Childhood. We subdivided the Vancouver adolescents according to whether they were Chinese immigrants to Canada, Canadian-born Chinese or Canadian-born non-Chinese. We compared the prevalence of asthma and wheezing among Chinese adolescents born in Canada, Chinese adolescents who had immigrated to Canada and Chinese adolescents living in China.

RESULTS

Of 7794 Chinese adolescents who met the inclusion criteria, 3058 were from Guangzhou, 2824 were from Beijing, and 1912 were from Hong Kong. Of 2235 adolescents in Vancouver, Canada, 475 were Chinese immigrants, 617 were Canadian-born Chinese, and 1143 were Canadian-born non-Chinese. The prevalence of current wheezing among boys ranged from 5.9% in Guangzhou to 11.2% in Canadian-born Chinese adolescents. For girls, the range was 4.3% in Guangzhou to 9.8% in Canadian-born Chinese adolescents. The prevalence of ever having had asthma ranged from 6.6% to 16.6% for boys and from 2.9% to 15.0% for girls. Prevalence gradients persisted after adjustment for other environmental variables (odds ratios for ever having had asthma among Canadian-born Chinese compared with native Chinese in Guangzhou: 2.72 [95% confidence interval 1.75-4.23] for boys and 5.50 [95% confidence interval 3.21-9.44] for girls; p < 0.001 for both). Among Chinese adolescents living in Vancouver, the prevalence of ever wheezing increased with duration of residence, from 14.5% among those living in Canada for less than 7 years to 20.9% among those living their entire life in Canada. The same pattern was observed for the prevalence of ever having had asthma, from 7.7% to 15.9%.

INTERPRETATION

Asthma symptoms in Chinese adolescents were lowest among residents of mainland China, were greater for those in Hong Kong and those who had immigrated to Canada, and were highest among those born in Canada. These findings suggest that environmental factors and duration of exposure influence asthma prevalence.

Early introduction of fish decreases the risk of eczema in infants

BACKGROUND

Atopic eczema in infants has increased in western societies. Environmental factors and the introduction of food may affect the risk of eczema.

AIMS

To investigate the prevalence of eczema among infants in western Sweden, describe patterns of food introduction and assess risk factors for eczema at 1 year of age.

METHODS

Data were obtained from a prospective, longitudinal cohort study of infants born in western Sweden in 2003; 8176 families were randomly selected and, 6 months after the infant's birth, were invited to participate and received questionnaires. A second questionnaire was sent out when the infants were 12 months old. Both questionnaires were completed and medical birth register data were obtained for 4921 infants (60.2% of the selected population).

RESULTS

At 1 year of age, 20.9% of the infants had previous or current eczema. Median age at onset was 4 months. In multivariable analysis, familial occurrence of eczema, especially in siblings (OR 1.87; 95% confidence interval (CI) 1.50 to 2.33) or the mother (OR 1.54; 95% CI 1.30 to 1.84), remained an independent risk factor. Introducing fish before 9 months of age (OR 0.76; 95% CI 0.62 to 0.94) and having a bird in the home (OR 0.35; 95% CI 0.17 to 0.75) were beneficial.

CONCLUSIONS

One in five infants suffer from eczema during the first year of life. Familial eczema increased the risk, while early fish introduction and bird keeping decreased it. Breast feeding and time of milk and egg introduction did not affect the risk.

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).

The predictive value of IgE as biomarker in asthma

BACKGROUND

The evidence for a causal relationship between allergens and asthma depends on epidemiologic findings showing a strong association between specific immunoglobulin E (IgE) antibodies or total IgE and asthma.

OBJECTIVE

To clarify the relationship between total serum IgE levels and asthma.

STUDY DESIGN

A cross-sectional study.

PATIENTS AND METHODS

A total of 562 asthmatic patients were included in the study, and their age range was from 17 to 52 years. The subjects included in the study were outpatients from the Asthma and Allergy Centre or Samara General Hospital outpatients Clinic. The diagnosis of asthma was performed by a specialist physician and was established according to the National Heart Blood and Lung Institute/World Health Organization (NHLBI/WHO) workshop on the Global Strategy for Asthma.

RESULTS

This study indicated that mean serum IgE level was 554 +/- 447 IU/mL in asthmatic patients, while that of the control population was 69 +/- 33 IU/mL. There was no overlap in the values of 95% confidence interval (CI) of higher control limit and lower asthmatic limit values. Addition of two standard deviations to the mean IgE value of the control group (134 IU/mL) does not overlap with the lower 95% CI of the asthmatic group. However, serum IgE was within normal values in 5.9% of asthmatic patients in our study population. There was an inverse correlation between serum IgE levels and forced expiratory volume in 1 second (FEV(1)) predicted percent for patients with asthma (r = -0.73, p < 0.0001). The predictive value of serum IgE in asthma was determined using Receiver Operating Characteristics (ROC) curve method. From the ROC curve, it can be seen that it is possible to get both high sensitivity and high specificity if the right cut-off value was chosen. In fact, a cut-off of 200 IU/mL would indicate sensitivity of 93% and specificity of 91% in this group of patients and control subjects. Following immunotherapy there was 36% reduction in total serum IgE level. The value of IgE was significantly reduced (p < 0.001) from 956 +/- 378 IU/mL at baseline to 613 +/- 194 IU/mL after treatment.

CONCLUSION

Serum IgE level was predictive in asthma, and it may be used to differentiate between asthmatic and non-asthmatic individuals in conjunction with other biomarkers. Specific immunotherapy reduced serum total IgE level in 36% of patients with asthma.

Meta-analysis of determinants for pet ownership in 12 European birth cohorts on asthma and allergies: a GA2LEN initiative

BACKGROUND

Studies on pet ownership as a risk or protective factor for asthma and allergy show inconsistent results. This may be on account of insufficient adjustment of confounding factors.

AIM

The objective of this study was to describe determinants of cat and dog ownership in European families with and without allergies.

METHODS

Within the EU-funded network of excellence GA(2)LEN, we performed meta-analyses with data from 12 ongoing European birth cohort studies on asthma and allergy. Each of the birth cohort studies enrolled between 485 and 4089 children. Pet ownership, allergic status (asthma, allergic rhinitis, eczema) of parents and siblings, parental education, access to ground floor, and number of people living at home were assessed by questionnaires.

RESULTS

Among the 25 056 families from seven European countries cats (14.9%) were more common than dogs (12.0%). Allergic family history significantly reduced the odds to own a cat (adjusted combined random-effect OR 0.91; 95% CI 0.85-0.99), or dog (0.90; 0.86-0.94). A higher parental educational level had even more pronounced effects on cat (0.84; 0.71-0.98), and dog ownership (0.61; 0.54-0.70). Elder siblings reduced the odds to own cats, but not dogs. Convenient ground access significantly increased the odds, whereas crowding at home was not associated with cat or dog ownership.

CONCLUSIONS

The chances to own a cat or dog were significantly reduced in allergic families, in parents with a higher educational level, and in homes without convenient ground access. In addition to parental allergies, social and housing factors should be considered as potential confounders in studies on pet exposure and allergic diseases.

Nonlinear relationship of mite allergen exposure to mite sensitization and asthma in a birth cohort

BACKGROUND

There is uncertainty about the nature of the relationship between mite allergen exposure during infancy and the expression of allergic diseases in childhood.

OBJECTIVE

We sought to explore the relationships between repeated measurements of mite allergen exposure during the first 5 years of life and clinical allergic disease outcomes at age 5 years.

METHODS

In a birth cohort of 516 at-risk children, 13 bed dust samples were collected between birth and 5 years of age and analyzed for mite allergen. At age 5 years, the presence of mite atopy was assessed based on skin prick test results, and clinical assessments for asthma, eczema, and wheeze were conducted. The association of allergen exposure with each clinical outcome was examined by means of logistic regression, with adjustments for potential confounders.

RESULTS

The lowest and highest mite exposure quintiles, expressed as mean allergen concentration averaged over 0 to 5 years, were associated with a lower prevalence of mite atopy and of asthma compared with intermediate levels of exposure. These relationships, when determined by using average allergen concentration over 0 to 18 months, were weaker.

CONCLUSIONS

This study demonstrates a nonlinear relationship between mite allergen exposure and clinical outcomes in this generally high mite allergen environment.

Cat ownership is a risk factor for the development of anti-cat IgE but not current wheeze at age 5 years in an inner-city cohort

BACKGROUND

Cat ownership is inversely associated with atopy and asthma in some areas of the world, but the relevance of cat ownership to allergic disease in the inner city is less known.

OBJECTIVE

We sought to evaluate the relationship between cat ownership and the development of early sensitization and wheeze.

METHODS

By using a prospective birth cohort study, Dominican and African American mothers living in New York City underwent repeated questionnaires about their child from birth to age 5 years. Sera collected from children at ages 2 (n = 323), 3 (n = 336), and 5 (n = 242) years were assayed for anti-cat IgE and anti-Fel d 1 IgG antibodies.

RESULTS

Cat ownership was a significant risk factor for the development of anti-cat IgE by age 2 years (risk ratio [RR], 6.4; 95% CI, 1.9-22) but not for anti-cat IgE development between the ages of 2 and 5 years (RR, 0.88; 95% CI, 0.24-2.3). Current wheeze was significantly more common among those children with anti-cat IgE at ages 3 (RR, 3.5; 95% CI, 2.1-6.0) and 5 (RR, 3.4; 95% CI, 2.3-4.9) years. Cat ownership was inversely associated with current wheeze at age 5 years among children without anti-cat IgE (RR, 0.26; 95% CI, 0.083-0.81). Among children with anti-cat IgE, a similar trend was observed (RR, 0.57; P = .044, Fisher exact test), although one with borderline statistical significance.

CONCLUSIONS

Despite a positive association with sensitization, cat ownership in this inner-city cohort was inversely associated with wheeze, potentially suggesting an IgE-independent protective mechanism in this community.

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.

Housing characteristics, home environmental factors and respiratory health in 14,729 Chinese children

BACKGROUND

Very few studies have assessed the relative impact of housing characteristics and home environmental factors on asthma and asthma-related symptoms in Chinese children who have lower rates of asthma. To our knowledge few studies have assessed respiratory symptoms and allergies in this context.

METHODS

To assess the effects of housing characteristics, pet keeping, home decorations and other indoor environmental factors on respiratory health of Chinese children. We studied a population of 14,729 children (1-13 years old) from 12 districts in Liaoning province, Northeast China. Information on respiratory health, housing characteristics, and environmental pollutions were obtained by a standard questionnaire from the American Thoracic Society.

RESULTS

Housing conditions, house adjacent to traffic or not, house with or without pollution source nearby, pet keeping, presence of pests and mold/water damage in the home, home decorations and exposure to environmental tobacco smoke (ETS) were associated with doctor-diagnosed asthma and asthma-related symptoms both in boys and girls. The vulnerability towards exposure to housing conditions and environmental factors differed between males and females. Among boys, the risk of respiratory morbidity appeared to be reduced in households with larger surface areas and more rooms; use of a ventilation device was strongly protective against persistent phlegm (OR=0.68; 95%CI: 0.48, 0.96). Asthma-related symptoms were more associated with different pets among girls than among boys. The presence of a cat in the household was associated with doctor-diagnosed asthma (OR=1.89; 95% CI, 1.11-3.20), current wheeze (OR=2.64; 95% CI, 1.52-4.59), persistent cough (OR=1.84; 95% CI, 1.18-2.87) and persistent phlegm (OR=2.17; 95% CI, 1.21-3.87) only among girls.

CONCLUSION

Living within the vicinity of a source of pollution, traffic, pet keeping, home decorations, pests, mold and ETS are important determinants of children's respiratory health in China.

Pediatric asthma

Asthma is one of the most common chronic illnesses affecting children. However, distinguishing true asthma from recurrent respiratory symptoms is often a challenge for primary care providers. Many risk factors can help predict persistent disease, including presence of allergies or eczema, family history, symptoms apart from obvious infection, and the severity of previous episodes. Because neither cure nor prevention is currently a viable option, the treatment is aimed at minimizing symptoms and maximizing asthma control.

Environmental factors influencing the prevalence of respiratory diseases and allergies among schoolchildren in Chiang Mai, Thailand

Air quality has seriously deteriorated as a consequence of population growth and urbanisation and respiratory diseases increased among residents of urban areas in Chiang Mai Province, Thailand. An International Study of Asthma and Allergies in Childhood (ISAAC) study was conducted among children attending schools located in the selected sites to assess the potential impacts of air pollution on health. The results showed that the prevalence of asthma was similar in all of the schools (approximately 5%; p = 1.000) but that the prevalence of rhinitis [24.3% (CI = 19.4-30.1) vs. 15.7% (CI = 10.3-23.0); p = 0.029] and atopic dermatitis [12.5% (CI = 9.1-16.8) vs. 7.2% (CI = 3.7-12.6); p = 0.093)] was higher in the urban schools, which were exposed to more pollution. Logistic regression analysis identified factors that may be involved, including air pollution, some components of the diet and contact with animals.

Effects of housing characteristics and home environmental factors on respiratory symptoms of 10,784 elementary school children from northeast china

BACKGROUND

Only few studies have assessed the relative impact of housing characteristics and home environmental factors on asthma and asthma-related symptoms in Chinese children, and to our knowledge, few studies have elaborated respiratory symptoms and allergies in this context.

OBJECTIVE

It was the aim of this study to assess the effects of housing characteristics, pet keeping, home decorations and other indoor environmental factors on respiratory health of Chinese children.

METHODS

We studied 10,784 children (6-13 years old) from 12 districts in Liaoning province, Northeast China. Information on respiratory health, housing characteristics and environmental pollution was obtained by a standard questionnaire from the American Thoracic Society.

RESULTS

Prevalence of asthma-related symptoms was higher for those living along the main stem of traffic, and for those with a house nearby a pollution source. Lower prevalence rates of respiratory morbidity were associated with households with a bigger area of residence and more rooms. Pet keeping was associated with doctor-diagnosed asthma (OR = 1.52; 95% CI 1.25-1.84). Home decorations also increased the risk of doctor-diagnosed asthma (OR = 1.72; 95% CI 1.45-2.04) and current asthma (OR = 1.43; 95% CI 1.06-1.93). Environmental tobacco smoke, pests and visible mold on walls were associated with the occurrence of asthma symptoms.

CONCLUSION

Home environmental factors are particularly important for the development of respiratory morbidity among children.

The New York City Puerto Rican asthma project: study design, methods, and baseline results

OBJECTIVE

We examined asthma risk factors among 274 Puerto Rican children born in New York to atopic mothers.

METHODS

We prospectively followed the cohort to measure aeroallergens in their homes and assess allergic sensitization. Baseline data are presented.

RESULTS

Maternal smoking was significantly higher among women born on the continental United States (25%) vs. those born elsewhere (11%). Cat ownership was more frequent among mainland-born women (15%) compared with those born in Puerto Rico (4%). While some aeroallergens were prevalent, few dust samples contained detectable dust mite allergens.

CONCLUSIONS

By following this cohort, we hope to identify the roles that socio-cultural factors play in the process of allergic sensitization.

Time trends of the prevalence of asthma and allergic disease in Austrian children

After a substantial increase in the prevalence of atopic disease in Europe, recent studies indicate that a plateau has been reached. However, variation across countries and age groups exists. We studied the prevalence and time trends of asthma and allergic disease among schoolchildren in Austria, a country with traditionally low rates of asthma, hay fever, and eczema. As part of the International Study of Asthma and Allergies in Childhood (ISAAC), symptoms and physician diagnoses of asthma and allergic disease of 13,399 Austrian children aged 6-7 yr and 1516 children aged 12-14 yr were surveyed between 1995 and 1997. A similar survey was conducted between 2001 and 2003. Among children aged 6-7 yr, significant increases were seen in the prevalence of physician-diagnosed asthma (+16%; p = 0.013), hay fever (+22%; p < 0.001), and eczema (+37%; p < 0.001) between 1995 and 2003. These changes were paralleled by an increase in the prevalence of symptoms typical for hay fever (itchy eyes and runny nose), but not by an increase in wheeze. Among children aged 12-14 yr, the lifetime prevalence of diagnosed asthma increased by 32%, of hay fever by 19%, and of eczema by 28% (all, p < 0.001). These changes were paralleled by increases in the prevalence of wheezing as documented by both questions before and after a video showing wheezing children but not by symptoms typical for hay fever such as itchy eyes and runny nose. In conclusion, in Austria, contrary to other European countries, the prevalence of asthma and allergic disease increased among schoolchildren. Additional studies are needed to continue monitoring the dynamics of the prevalence of asthma and allergic disease in Austria and to explore trends in their risk factors.

Predictivity of allergic sensitization (RAST) for the onset of allergic diseases in adults

BACKGROUND

Specific IgE antibodies are often detected without any clinical manifestation of allergies. We aimed to analyse the predictivity of allergic sensitization for incident symptoms of allergic diseases in adults during a 10-year follow-up.

METHODS

In 1994/95 specific IgE antibodies against five common inhalant allergens (grass pollen, birch pollen, house dust mite, cat dander and Cladosporium) were diagnosed by radioallergosorbent test in 4178 adults aged 25-74 years. A subset of 2656 participants could be re-evaluated in 2004/05. Information on socio-economic factors and medical history, including data on atopic diseases, was assessed by a combination of a personal interview and a self-administered questionnaire. Logistic regression models were applied to study associations between allergic sensitization and incident allergic diseases.

RESULTS

Allergic sensitization was an important predictor for incident hay fever (OR 7.95, CI 95% 4.64-13.62) and asthma (OR 1.82, CI 95% 1.29-2.57). Specific IgE antibodies were mainly related to outdoor allergens (grass and birch pollen) for hay fever and indoor allergens (mite and cat dander) for asthma, while for atopic dermatitis no specific IgE antibodies were identified as major predictors.

CONCLUSIONS

Allergic sensitization not only covers clinically apparent allergies, but indicates a prognostic factor for later allergies, even in adulthood.

Primary prevention of allergy: avoiding risk or providing protection?

Primary prevention strategies of allergy so far have been aimed to fight allergy causes, by avoiding risk factors and inhibiting their mechanisms of action. The results of trials testing food or airborne allergen avoidance as a prevention strategy were, however, rather disappointing. A reverse approach for primary prevention of allergies aims to facilitate exposure to protecting factors which promote the induction of immunologic tolerance against innocuous antigens. These factors are associated with farming environment and a 'traditional lifestyle', but identification of these factors is quite difficult. Major candidates include food-borne microbes, helminths or their components, which are able to stimulate mucosal immunity, particularly in the gut. Similarly, new preventive and therapeutic strategies are being tested to induce specific food-allergen oral tolerance through the ingestion of progressively increasing doses of the offending food. This shifting of allergy prevention research from avoidance to tolerance induction will hopefully allow us to reverse the epidemic trend of allergy diseases.

Urticaria is associated with birch-pollen sensitization

Urticaria is a common condition, seldom of allergic origin. It is however not always possible to find the provoking allergen. The aim of the present study was to analyze if there was a relationship between urticaria and sensitization to common airborne allergens. A representative sample of 402 12 to 13-yr-old children answered a questionnaire on allergic diseases, 397 were interviewed by the study nurse and 371 underwent skin prick tests to cat, dog, horse, birch, timothy-grass, house dust mites and Cladosporium mould. Specific IgE-antibodies were analyzed to birch pollen and cat dander. Urticaria was more common in sensitized children, but the relationship between urticaria and sensitization was only statistically significant for birch pollen sensitization (OR 1.99, 95% CL 1.04-3.83), when tested in a multiple logistic regression model with the specified allergens as independent variables. A similar pattern was seen for birch-specific IgE-antibody levels, which was higher in children reporting urticaria than in those without. IgE-levels to cat dander did not show such a difference. Urticaria was statistically significantly associated with sensitization to birch-pollen, but not to other common inhalant allergens. We propose that intake of birch-pollen cross-reactive food-stuffs may be a neglected cause of urticaria and relapsing urticaria, in birch-pollen sensitized subjects.

A prospective study of allergy development in 158 children and 128 adults with new extensive exposure to furred animals

BACKGROUND

There is still controversy over whether exposure to furred animals increases or decreases the risk of developing sensitization and allergic symptoms to such animals, and there is a need for further knowledge on this subject.

OBJECTIVE

The aim of this study was to follow allergy development in relation to new extensive exposure to furred animals in adults and children.

METHODS

A total of 286 individuals, 128 parents and 158 children, were recruited from 68 families who intended to buy a dog or a cat, or where one child of the family intended to start riding a horse. Subjects were examined before the new allergen exposure and once a year thereafter for 5 years, in all at six occasions, and they also completed questionnaires covering allergy symptoms. Serum IgE antibodies to cat, dog and horse were determined each year, and fur allergens from beds and living rooms were analysed.

RESULTS

Two-hundred and fifty-six study subjects remained for evaluation, 37 of whom showed signs of allergic sensitization at the start of the study. Four children (11%) in this pre-sensitized group developed IgE antibodies to their new animal and six (16%) to another animal. Among the 219 participants who were not sensitized when entering the study, one male adult (0.4%) developed a sensitization to his new animal, and nobody developed sensitization to other animals. Pre-sensitized individuals had significantly more allergic symptoms at the study start, but the symptom scores did not change over time.

CONCLUSIONS

When the first year of a human's life has passed, we have no strong evidence to recommend avoidance of a domestic animal in order to prevent new allergy development, even if there are known allergies in the family or if the individual is sensitized and has allergic symptoms to another allergen. Five years exposure to new fur allergens does not seem to influence sensitization to these animals in either sensitized or non-sensitized children and adults.

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.

Cockroach allergen levels and associations with cockroach-specific IgE

BACKGROUND

Among inner-city children with asthma, cockroach allergen exposure has been associated with allergic sensitization.

OBJECTIVE

We hypothesized that cockroach allergen levels in homes would be associated with sensitization to cockroach allergens in children.

METHODS

From a low-income preschool program, 341 four-year-old children selected on the basis of the willingness of their caregivers to participate in the study were enrolled. Dust from their beds and kitchens were analyzed for cockroach (Bla g 2), mouse (mouse urinary proteins), and cat allergens (Fel d 1). Serum samples were analyzed for allergen-specific IgE antibodies by immunoassay.

RESULTS

Bla g 2 levels >1 U/g in children's bed and kitchen dust samples were independently associated with cockroach-specific IgE (odds ratio [OR], 2.7; 95% CI, 1.1-6.4; and OR, 3.4; 95% CI, 1.2-9.4, respectively), adjusting for sex, ethnicity, asthma, pet ownership, mother's allergic sensitization, environmental tobacco smoke, and having lived in other homes. Bla g 2 was associated (OR, 3.6; 95% CI, 1.0-13.1) with cockroach-specific IgE among children with asthma. Among children without asthma, the ORs were similar (OR, 3.0; 95% CI, 0.9-10.3), but the association was not statistically significant.

CONCLUSION

Concentrations of the major cockroach allergen, Bla g 2, in settled dust were associated with cockroach-specific IgE independent of other factors in a cohort of 4-year-old inner-city children.

Risk factors for asthma at 3.5 and 7 years of age

BACKGROUND

It has been suggested that factors in early life including exposure to allergens and microbes may influence the development of asthma.

OBJECTIVE

To identify risk factors for asthma in early childhood. Methods Eight-hundred and seventy-one children of European mothers were enrolled at birth, of whom 385 (44.2%) were born small for gestational age (SGA) and 486 were appropriate for gestational age (AGA). Data were collected at birth, 12 months, 3.5 years of age (y) and 7 y. The outcome of interest (current wheeze) was defined as a positive response to the question: 'Has your child had wheezing or whistling in the chest in the last 12 months?'

RESULTS

Participation rate was 85.4% at 1 y, 63.1% at 3.5 y and 68.0% at 7 y. The prevalence of asthma was 23.8% at 3.5 y and 18.1% at 7 y. Antibiotic use in the first year of life and day care in the first year of life were associated with increased risk of wheeze at 7 y [odds ratio (OR)=4.3 95% confidence interval (CI) (1.8-10.1) and OR=2.8 95% CI (1.2-6.5), respectively], but not at 3.5 y. Exposure to dogs was a risk factor for asthma at both ages [OR=2.1 95% CI (1.1-3.8)] as was sleeping on a used cot mattress in the first year of life [OR=1.8 95% CI (1.0-3.2)].

CONCLUSIONS

There was a significant association between antibiotic use and day care in the first year of life and wheezing at 7 y but not at 3.5 y. This strengthens the argument that these factors increase the risk of asthma. We have also made the novel observation that sleeping on a used mattress in the first year of life is a risk factor for wheezing at 3.5 and 7 y. Capsule summary This prospective study of 871 children made the novel observation that sleeping on a used mattress in the first year of life was a risk factor for wheezing at 3.5 and 7 y.

Prevention of allergic diseases

The prevalence of asthma and allergic diseases has increased in recent years, particularly in the industrialized world. Allergic disease begins to manifest in the first years of life. The disorder usually manifests initially in the form of food allergy and atopic dermatitis, followed in later stages by respiratory allergy with rhinitis and/or asthma. This has led to the adoption of preventive measures in those children with a high risk of atopy, based on the following considerations: 1) A family history of allergic diseases (asthma, eczema, and/or allergic rhinitis); 2) A personal history of atopy such as atopic dermatitis, particularly when associated to food allergy; and 3) The existence of allergic sensitization, particularly to pneumoallergens, of early or late onset, but persistent during childhood. Prevention is established at three different levels: primary prevention, avoiding sensitization; secondary prevention, avoiding appearance of the disease; and tertiary prevention, avoiding the symptoms. The present study discusses current knowledge of prevention and its efficacy, with mention of the importance of breastfeeding and the use of pre- and probiotics for securing adequate prevention.

Interactive effect of family history and environmental factors on respiratory tract-related morbidity in infancy

BACKGROUND

Family and environmental factors affect the development of respiratory morbidity. How these factors interact is unclear.

OBJECTIVE

We sought to clarify the interactive effect of family history of asthma and environmental factors on the occurrence of respiratory morbidity.

METHODS

Two hundred twenty-one infants with a positive family history of asthma (PFH) and 308 with a negative family history of asthma (NFH) were prenatally selected and followed until the age of 2 years. Exposure to environmental factors and the occurrence of respiratory morbidity were recorded. By using multiple logistic regression analysis, increased risk was expressed in odds ratios (ORs) adjusted for relevant covariables.

RESULTS

Infants with a PFH had more respiratory morbidity than infants with an NFH. Adjusted ORs ranged from 1.7 (95% CI, 1.0-2.8) for expiratory wheezing to 4.9 (95% CI, 1.7-13.6) for croup. Parental smoking increased the OR of a PFH for wheezing ever (OR, 5.8 [95% CI, 2.5-13.8]) and attacks of wheezing (OR, 6.8 [95% CI, 2.7-16.9]), as did Der p 1 (OR, 10.2 [95% CI, 2.8-36.3] and OR, 7.1 [95% CI, 7.1-21.0], respectively). Exposure to both parental smoking and Der p 1 further increased this OR (OR, 30.8 [95%, CI, 6.9-137.2] and OR, 26.2 [95% CI, 5.9-115.6], respectively). Breast-feeding decreased the ORs of PFH for tonsillitis and acute otitis media: the increased ORs for these diagnoses in formula-fed infants with PFHs versus those with NFHs (OR, 9.2 [95% CI, 2.1-39.7] and OR, 2.9 [95% CI, 1.1-7.2], respectively) was attenuated in breast-fed infants (OR, 1.8 [95% CI, 0.8-3.8] and OR, 0.7 [95% CI, 0.4-1.3]).

CONCLUSION

Parental smoking and Der p 1 increase the effect of a PFH on respiratory morbidity. Breast-feeding reduces this effect.

CLINICAL IMPLICATIONS

Extra attention should be given to stimulate mothers to breast-feed their children in case they cannot stop smoking or taking sanitation measures.