Exposure to pets and atopic dermatitis during the first two years of life. A cohort study

English version of clinical practice guidelines for the management of atopic dermatitis 2024

This is the English version of the 2024 clinical practice guidelines for the management of atopic dermatitis (AD). AD is a disease characterized by relapsing eczema with pruritus as a primary lesion. A crucial aspect of AD treatment is the prompt induction of remission via the suppression of existing skin inflammation and pruritus. To achieve this, topical anti-inflammatory drugs, such as topical corticosteroids, tacrolimus ointment, delgocitinib ointment, and difamilast ointment, have been used. However, the following treatments should be considered in addition to topical therapy for patients with refractory moderate-to-severe AD: oral cyclosporine, subcutaneous injections of biologics (dupilumab, nemolizumab, tralokinumab), oral Janus kinase inhibitors (baricitinib, upadacitinib, abrocitinib), and phototherapy. In these revised guidelines, descriptions of five new drugs, namely, difamilast, nemolizumab, tralokinumab, upadacitinib, and abrocitinib, have been added. The guidelines present recommendations to review clinical research articles, evaluate the balance between the advantages and disadvantages of medical activities, and optimize medical activity-related patient outcomes with respect to several important points requiring decision-making in clinical practice.

Smoke exposure and childhood atopic eczema and food allergy: A systematic review and meta-analysis

BACKGROUND

There is no consensus on the effect of timing and type of smoke exposure on early allergy development. This study aimed to determine the relationship between early eczema or food allergy/hypersensitivity development in children by firstly investigating the effect of smoke exposure across critical development periods and secondly by analyzing effects of parental atcive or passive smoking.

METHODS

Four databases (PubMed, Web of Science, Scopus and Embase) were searched in May 2022 and assessed by two independent reviewers. Case-control, cross-sectional or cohort studies reporting on smoke exposure from preconception to postnatal periods and atopic eczema, food allergy and/or hypersensitivity outcomes by age 3 years were included. The Newcastle-Ottawa Scale was used to assess study quality. Random effects model was used to estimate the pooled risk ratios.

RESULTS

From 1689 identified records, 32 studies with nearly 190,000 subjects were included. Parental smoking during preconception, pregnancy and postnatal periods was generally not associated with the risk of eczema, food allergy and food sensitisation development by age 3 years. Maternal active smoking during pregnancy was negatively associated with self-reported doctor diagnosis of eczema (RR = 0.87, 95% CI 0.77-0.98; I2  = 50.56) and maternal passive smoking during pregnancy was positively associated with clinician assessment of eczema in one study (RR = 1.38; 95% CI 1.06-1.79).

CONCLUSION

Our findings highlighted the importance of in utero programming in early-life allergy development. Despite the weak evidence, our results suggest pregnant women should minimise their contact with second-hand smoke to prevent offspring eczema development. There is a need for greater utilisation of objective allergy assessments in future studies.

English Version of Clinical Practice Guidelines for the Management of Atopic Dermatitis 2021

This is the English version of the Clinical Practice Guidelines for the Management of Atopic Dermatitis 2021. Atopic dermatitis (AD) is a disease characterized by relapsing eczema with pruritus as a primary lesion. In Japan, from the perspective of evidence-based medicine, the current strategies for the treatment of AD consist of three primary measures: (i) use of topical corticosteroids, tacrolimus ointment, and delgocitinib ointment as the main treatment of the inflammation; (ii) topical application of emollients to treat the cutaneous barrier dysfunction; and (iii) avoidance of apparent exacerbating factors, psychological counseling, and advice about daily life. In the present revised guidelines, descriptions of three new drugs, namely, dupilumab, delgocitinib, and baricitinib, have been added. The guidelines present recommendations to review clinical research articles, evaluate the balance between the advantages and disadvantages of medical activities, and optimize medical activity-related patient outcomes with respect to several important points requiring decision-making in clinical practice.

High Incidence of Atopic Dermatitis among Children Whose Fathers Work in Primary Industry: The Japan Environment and Children's Study (JECS)

The hygiene hypothesis assumes a low incidence of allergic diseases in families engaging in farming work. However, a few studies have indicated rural life as a potential risk factor for atopic dermatitis (AD). Using a large Japanese birth cohort dataset, we calculated the accumulated incidence of AD in children aged 6 months and 1, 2, and 3 years by family business and the hazard ratio. We adjusted for confounding factors. The father's job was considered the family business. We analysed data on 41,469 father-child pairs at 6 months of age, 40,067 pairs at 1 year, 38,286 pairs at 2 years, and 36,570 pairs at 3 years. We found the highest accumulated incidence of AD among children with fathers engaged in primary industry, with 2.5% at the age of 6 months, 6.6% at 1 year, 12.0% at 2 years, and 15.4% at 3 years. Among primary industry occupations, forestry was associated with the highest incidence of AD across these ages. The hazard ratio of AD was also highest for children whose family business was primary industry. In conclusion, the highest incidence and hazard ratio of AD were observed among children whose fathers worked in primary industry.

Application of Epidemiology and Principles of Herd/Flock Health for the Exotic Animal Veterinarian

Against a backdrop of climate change and epidemics, the exotic animal veterinarian is well positioned to detect emerging and exotic disease threats, prevent and control zoonotic diseases, and identify antimicrobial resistance. Within the traditional context of animal and public health, epidemiology has had a focus on veterinary preventive health and in disease investigation and control particularly in food animal and safety application. The understanding of preventive health management and veterinary epidemiology expands the repertoire of the clinical veterinarian to advise and implement and evaluate group animal health programs and biosecurity measures as well as conduct disease investigations.

Effect of Exposure to Cats and Dogs on the Risk of Asthma and Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Controversies persist regarding whether exposure to cat or dog increases the risk of asthma and allergic rhinitis.

OBJECTIVE

This meta-analysis aimed to assess the associations between exposure to cats or dogs and the development of asthma and allergic rhinitis.

METHODS

A systematic review was performed to identify case-control and cohort studies before May 2019, evaluating the association between exposure to cats and dogs and the risk of asthma and rhinitis. The risk of bias was assessed using the Newcastle-Ottawa Scale. The odds ratios (ORs) and risk ratios (RRs) were pooled for case-control and cohort studies, respectively. Subgroup analyses were performed on prespecified study-level characteristics.

RESULTS

The meta-analysis of 34 cohort studies showed a protective role of exposure to cats [RR: 0.88, 95% confidence interval (CI): 0.77-0.99] or dogs (RR: 0.85, 95% CI: 0.73-0.97) in the development of asthma. The subgroup analysis of birth cohort (RR: 0.74, 95% CI: 0.56-0.93) and children population (RR: 0.83, 95% CI: 0.70-0.96) also suggested a favorable role of exposure to dogs in the development of asthma. Pooled evidence from 13 case-control studies indicated no significant impact of cats (OR: 1.66, 95% CI: 0.39-2.94) and dogs (OR: 1.22, 95% CI: 0.92-1.52) on the development of asthma. A pooled analysis of five cohort studies showed a favorable effect of exposure to cats (RR: 0.60, 95% CI: 0.33-0.86) or dogs (RR: 0.68, 95% CI 0.44-0.90) on the development of allergic rhinitis.

CONCLUSION

The findings indicated a protective effect of exposure to cats and dogs, especially ownership, on the development of asthma and allergic rhinitis.

Clinical practice guidelines for the management of atopic dermatitis 2018

Atopic dermatitis (AD) is a disease characterized by relapsing eczema with pruritus as a primary lesion. The current strategies to treat AD in Japan from the perspective of evidence-based medicine consist of three primary measures: (i) the use of topical corticosteroids and tacrolimus ointment as the main treatment for the inflammation; (ii) topical application of emollients to treat the cutaneous barrier dysfunction; and (iii) avoidance of apparent exacerbating factors, psychological counseling and advice about daily life. The guidelines present recommendations to review clinical research articles, evaluate the balance between the advantages and disadvantages of medical activities, and optimize medical activity-related patient outcomes with respect to several important points requiring decision-making in clinical practice.

Consensus document on dog and cat allergy

The prevalence of sensitization to dogs and cats varies by country, exposure time and predisposition to atopy. It is estimated that 26% of European adults coming to the clinic for suspected allergy to inhalant allergens are sensitized to cats and 27% to dogs. This document is intended to be a useful tool for clinicians involved in the management of people with dog or cat allergy. It was prepared from a consensus process based on the RAND/UCLA method. Following a literature review, it proposes various recommendations concerning the diagnosis and treatment of these patients, grounded in evidence and clinical experience. The diagnosis of dog and cat allergy is based on a medical history and physical examination that are consistent with each other and is confirmed with positive results on specific IgE skin tests. Sometimes, especially in polysensitized patients, molecular diagnosis is strongly recommended. Although the most advisable measure would be to avoid the animal, this is often impossible and associated with a major emotional impact. Furthermore, indirect exposure to allergens occurs in environments in which animals are not present. Immunotherapy is emerging as a potential solution to this problem, although further supporting studies are needed.

Atopic Dermatitis: Disease Background and Risk Factors

Multiple risk factors have been associated with the development of atopic dermatitis (AD). Recent advances in understanding the role of genetics in this disease have been made, with discovery of the filaggrin (FLG) gene as the most notable so far. In addition to FLG gene mutations as a risk factor for AD, a positive family history of atopic or allergic disease in either parent, has been shown to confer a greater risk of developing AD. Atopic dermatitis usually presents early in life and is thought to represent the initial-step in the "atopic march" which is characterized by the development of other atopic diseases later in life such as asthma, allergic rhinitis and/or rhinoconjunctivitis, food allergies and hay fever. Other comorbid diseases that have been associated with AD include increase risk of viral and bacterial skin infections, neuropsychiatric diseases such as attention-deficit hyperactivity disorders (ADHD) and autistic spectrum disorder (ASD). Patients with AD, have also been found to have worse sleep quality overall compared to patients without AD. In this chapter, we will discuss the risk factors associated with development of atopic dermatitis as well as the most commonly reported comorbidities in patients with this disease.

Critical assessment of the research outcomes of European birth cohorts: linking environmental factors with non-communicable diseases

OBJECTIVES

The objective of this review paper was to stimulate collaborative discussions toward the development of a general concept of an open source protocol for a feasible and efficient longitudinal birth cohort study exploring non-communicable diseases (NCDs), their multifactorial etiology and relations between various risk factors.

STUDY DESIGN

The present paper systematically reviews the design of existing birth cohorts in Europe containing environmental exposure data, and assesses a quantity and quality of their research outcomes as their potential to be an effective tool for studying non-communicable diseases and their risk factors.

METHODS

European birth cohorts with more than 3000 participants have been included in the study. A total number of scientific papers published in the internationally recognized journals and their impact factors and citation records were evaluated for all cohorts as surrogates for their efficiency to contribute to NCDs understanding and thus their prevention.

RESULTS

The birth cohorts contributing most significantly to the NCD understanding shared common features: (i) study size between 10,000 and 15,000 mother-child pairs; (ii) repeated assessment of children from prenatal into adulthood; and (iii) availability of biological samples. Smaller cohorts and cohorts with a specific focus generated a lower number of publications; however, these often received considerably a higher number of citations.

CONCLUSIONS

General cohort studies with 10,000-15,000 mother-child pairs allow a broader context interpretation, publish a higher number of articles, and often lead to the formation of infrastructures for 'spin-off (nested) studies'.

Air pollution and cytokine responsiveness in asthmatic and non-asthmatic children

Epidemiological studies indicate that asthmatic children are more susceptible to traffic-related air pollution exposure than non-asthmatic children. Local and systemic inflammation in combination with oxidative stress have been suggested as a possible susceptibility factor. We investigated effect modification by asthma status for the association between air pollution exposure and systemic effects using whole blood cytokine responsiveness as an inflammatory marker. The study was nested within the two German birth cohort studies GINIplus and LISAplus and initially designed as a random sub-sample enriched with asthmatic children. Using data from 27 asthmatic and 59 non-asthmatic six-year-old children we measured the production of Interleukin-6 (IL)-6, IL-8, IL-10, monocyte chemotactic protein-1 (MCP-1), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in whole blood after ex-vivo stimulation with urban particulate matter (EHC-93). Air pollution exposure (nitrogen dioxide (NO2), nitrogen oxides (NOx), particulate matter with an aerodynamic diameter <10μm (PM10), particulate matter with an aerodynamic diameter <2.5μm (PM2.5mass), coarse particulate matter (PMcoarse) and PM2.5absorbance (PM2.5abs)) was modelled for children´s home addresses applying land-use regression. To assess effect modification by asthma status linear regression models with multiplicative interaction terms were used. In asthmatics exposure to NO2 was associated with higher production of pro-inflammatory cytokines: adjusted means ratio (MR) 2.22 (95% confidence interval 1.22-4.04) for IL-6 per 2.68µg/m³ NO2. The interaction term between asthma status and NO2 exposure was significant. Results for NOx, PM10, PM2.5mass and PM2.5abs were in the same direction. No association between air pollution and cytokine responsiveness was found in the group of non-asthmatic children and in the overall group. Traffic-related air pollution exposure is associated with higher pro-inflammatory cytokine responsiveness in whole blood of asthmatic children.

New insights into the epidemiology of childhood atopic dermatitis

There is a growing desire to explain the worldwide rise in the prevalence of atopic dermatitis (AD). Trend data on the burden of AD suggest that the picture in the developing world may soon resemble that of wealthier nations, where AD affects over 20% of children. This, combined with significant variations in prevalence within countries, emphasizes the importance of environmental factors. Many hypotheses have been explored, from the modulation of immune priming by hygiene, gut microbiota diversity, and exposure to endotoxins through farm animals to the effects of pollution, climate, and diet. The discovery of the filaggrin skin barrier gene and its importance in AD development and severity has brought the focus on gene-environment interactions and the identification of environmental factors that impact on skin barrier function. This article reviews our current understanding of the epidemiology of AD, with an emphasis on the findings reported in the international literature over the last 5 years.

Air pollution and respiratory infections during early childhood: an analysis of 10 European birth cohorts within the ESCAPE Project

BACKGROUND

Few studies have investigated traffic-related air pollution as a risk factor for respiratory infections during early childhood.

OBJECTIVES

We aimed to investigate the association between air pollution and pneumonia, croup, and otitis media in 10 European birth cohorts--BAMSE (Sweden), GASPII (Italy), GINIplus and LISAplus (Germany), MAAS (United Kingdom), PIAMA (the Netherlands), and four INMA cohorts (Spain)--and to derive combined effect estimates using meta-analysis.

METHODS

Parent report of physician-diagnosed pneumonia, otitis media, and croup during early childhood were assessed in relation to annual average pollutant levels [nitrogen dioxide (NO2), nitrogen oxide (NOx), particulate matter≤2.5 μm (PM2.5), PM2.5 absorbance, PM10, PM2.5-10 (coarse PM)], which were estimated using land use regression models and assigned to children based on their residential address at birth. Identical protocols were used to develop regression models for each study area as part of the ESCAPE project. Logistic regression was used to calculate adjusted effect estimates for each study, and random-effects meta-analysis was used to calculate combined estimates.

RESULTS

For pneumonia, combined adjusted odds ratios (ORs) were elevated and statistically significant for all pollutants except PM2.5 (e.g., OR=1.30; 95% CI: 1.02, 1.65 per 10-μg/m3 increase in NO2 and OR=1.76; 95% CI: 1.00, 3.09 per 10-μg/m3 PM10). For otitis media and croup, results were generally null across all analyses except for NO2 and otitis media (OR=1.09; 95% CI: 1.02, 1.16 per 10-μg/m3).

CONCLUSION

Our meta-analysis of 10 European birth cohorts within the ESCAPE project found consistent evidence for an association between air pollution and pneumonia in early childhood, and some evidence for an association with otitis media.

Air pollution exposure and lung function in children: the ESCAPE project

BACKGROUND

There is evidence for adverse effects of outdoor air pollution on lung function of children. Quantitative summaries of the effects of air pollution on lung function, however, are lacking due to large differences among studies.

OBJECTIVES

We aimed to study the association between residential exposure to air pollution and lung function in five European birth cohorts with a standardized exposure assessment following a common protocol.

METHODS

As part of the European Study of Cohorts for Air Pollution Effects (ESCAPE) we analyzed data from birth cohort studies situated in Germany, Sweden, the Netherlands, and the United Kingdom that measured lung function at 6-8 years of age (n = 5,921). Annual average exposure to air pollution [nitrogen oxides (NO2, NOx), mass concentrations of particulate matter with diameters < 2.5, < 10, and 2.5-10 μm (PM2.5, PM10, and PMcoarse), and PM2.5 absorbance] at the birth address and current address was estimated by land-use regression models. Associations of lung function with estimated air pollution levels and traffic indicators were estimated for each cohort using linear regression analysis, and then combined by random effects meta-analysis.

RESULTS

Estimated levels of NO2, NOx, PM2.5 absorbance, and PM2.5 at the current address, but not at the birth address, were associated with small decreases in lung function. For example, changes in forced expiratory volume in 1 sec (FEV1) ranged from -0.86% (95% CI: -1.48, -0.24%) for a 20-μg/m3 increase in NOx to -1.77% (95% CI: -3.34, -0.18%) for a 5-μg/m3 increase in PM2.5.

CONCLUSIONS

Exposure to air pollution may result in reduced lung function in schoolchildren.

Pet exposure and risk of atopic dermatitis at the pediatric age: a meta-analysis of birth cohort studies

BACKGROUND

Findings on pet exposure and the risk of atopic dermatitis (AD) in children are inconsistent.

OBJECTIVE

With the aim to summarize the results of exposure to different pets on AD, we undertook a meta-analysis of epidemiologic studies on this issue.

METHODS

In August 2012, we conducted a systematic literature search in Medline and Embase. We included analytic studies considering exposure to dogs, cats, other pets, or pets overall during pregnancy, infancy, and/or childhood, with AD assessment performed during infancy or childhood. We calculated summary relative risks and 95% CIs using both fixed- and random-effects models. We computed summary estimates across selected subgroups.

RESULTS

Twenty-six publications from 21 birth cohort studies were used in the meta-analyses. The pooled relative risks of AD for exposure versus no exposure were 0.72 (95% CI, 0.61-0.85; I(2) = 46%; results based on 15 studies) for exposure to dogs, 0.94 (95% CI, 0.76-1.16; I(2) = 54%; results based on 13 studies) for exposure to cats, and 0.75 (95% CI, 0.67-0.85; I(2) = 54%; results based on 11 studies) for exposure to pets overall. No heterogeneity emerged across the subgroups examined, except for geographic area.

CONCLUSION

This meta-analysis reported a favorable effect of exposure to dogs and pets on the risk of AD in infants or children, whereas no association emerged with exposure to cats.

Controversial role of pets in the development of atopy in children

BACKGROUND

Exposure to environmental allergens originating from different sources has been implicated in the sensitization to the respective allergens and development of atopic diseases. Keeping domestic animals is associated with exposure to relevant allergens but there are controversial data whether this exposure promotes or protects from the development of atopy.

DATA SOURCES

We herein reviewed the literature regarding the available data for the exposure to pets (cats and/or dogs) and the development of atopy. For this purpose, we searched the PubMed database.

RESULTS

This review attempts to answer the following questions that arise from the daily practice and the relevant studies, which are: a) is pet keeping associated with sensitization? b) is there an association between keeping pets and the development of asthma, allergic rhinitis and eczema, and, c) what is the underlying mechanism of any possible protective association? Despite the fact that several studies and meta-analyses have been conducted to explore the role of pets in the development of atopy, there are still conflicting pieces of evidence. It seems that there are different effects depending on the type of pets, the time and duration of exposure, and the genetic background of the individual.

CONCLUSION

Further appropriately designed birth cohort studies are needed to explore whether exposure to relevant allergens from pets promotes or protects from the development of atopy.

Glutathione-S-transferase P1, early exposure to mould in relation to respiratory and allergic health outcomes in children from six birth cohorts. A meta-analysis

BACKGROUND

There are conflicting study results regarding the association of exposure to visible mould and fungal components in house dust with respiratory and allergic diseases in children. It has been suggested that functional polymorphisms of the GSTP1 gene may influence the risk for allergic disorders through an impaired defence against oxidant injury.

METHODS

We examined in six birth cohorts of over 14 000 children whether the association between early exposure to reported mould at home in relation to respiratory and allergic diseases is modified by a single nucleotide polymorphism of the GSTP1 gene.

RESULTS

We observed a positive association of mould exposure with nasal symptoms (2-10 year) aOR: 1.19 (1.02-11.38). Further, there was a borderline significant increased risk of rhinoconjunctivitis (6-8 year) in children homozygous for the minor allele Val/Val, aOR: 1.25 (0.98-1.60). In stratified analyses, subjects homozygous for the minor allele and exposed to mould at home were at increased risk for early wheezing aOR: 1.34 (1.03-1.75), whereas the major allele may confer susceptibility for later nasal outcomes, (6-8 year) aOR: 1.20 (1.00-1.45) and (2-10 year) aOR: 1.30 (1.04-1.61), respectively. For none of the health outcomes studied, we found gene by environment interactions.

CONCLUSION

A genetic influence of the GSTP1 gene cannot be ruled out, but the magnitude of the effect is a matter of further research. In conclusion, the interplay between gene and environments is complex and remains subject of further study.

Surveillance of home environment in children with atopic dermatitis: a questionnaire survey

BACKGROUND

The increasing prevalence of atopic dermatitis (AD) suggests a role for environmental factors in triggering a genetic predisposition in sufferers.

OBJECTIVE

The purpose of this study was to investigate home environmental factors related to AD severity.

METHODS

We conducted a questionnaire survey about the home environmental factors in 380 children from two daycare centers and the Samsung Medical Center outpatient clinic. AD was diagnosed by Hanifin and Rajka's criteria and its severity was assessed by the Severity Scoring of Atopic Dermatitis index. Children were divided into normal control group, mild AD group and severe AD group. Home environmental factors were compared among the three groups and were statistically analyzed using analysis of variance, Chi-square test, Fisher's exact test, and multiple logistic analysis.

RESULTS

Indoor remodeling activities, such as painting (p = 0.004), floor covering (p = 0.001) and wallpaper changing (p = 0.002) were associated with severity of AD. Those in the severe AD group were more likely to live in an apartment (p < 0.001). Severe AD was observed more frequently when the monthly income of household (p = 0.027) and final educational status of mother (p = 0.001) were higher.

CONCLUSION

Some home environmental factors were associated with AD severity, but its causal relationship is not clear. Further research is needed to confirm these associations and to clarify whether they are causative.

European birth cohorts for environmental health research

BACKGROUND

Many pregnancy and birth cohort studies investigate the health effects of early-life environmental contaminant exposure. An overview of existing studies and their data is needed to improve collaboration, harmonization, and future project planning.

OBJECTIVES

Our goal was to create a comprehensive overview of European birth cohorts with environmental exposure data.

METHODS

Birth cohort studies were included if they a) collected data on at least one environmental exposure, b) started enrollment during pregnancy or at birth, c) included at least one follow-up point after birth, d) included at least 200 mother-child pairs, and e) were based in a European country. A questionnaire collected information on basic protocol details and exposure and health outcome assessments, including specific contaminants, methods and samples, timing, and number of subjects. A full inventory can be searched on www.birthcohortsenrieco.net.

RESULTS

Questionnaires were completed by 37 cohort studies of > 350,000 mother-child pairs in 19 European countries. Only three cohorts did not participate. All cohorts collected biological specimens of children or parents. Many cohorts collected information on passive smoking (n = 36), maternal occupation (n = 33), outdoor air pollution (n = 27), and allergens/biological organisms (n = 27). Fewer cohorts (n = 12-19) collected information on water contamination, ionizing or nonionizing radiation exposures, noise, metals, persistent organic pollutants, or other pollutants. All cohorts have information on birth outcomes; nearly all on asthma, allergies, childhood growth and obesity; and 26 collected information on child neurodevelopment.

CONCLUSION

Combining forces in this field will yield more efficient and conclusive studies and ultimately improve causal inference. This impressive resource of existing birth cohort data could form the basis for longer-term and worldwide coordination of research on environment and child health.

Meta-analysis of mould and dampness exposure on asthma and allergy in eight European birth cohorts: an ENRIECO initiative

BACKGROUND

Several cross-sectional studies during the past 10 years have observed an increased risk of allergic outcomes for children living in damp or mouldy environments.

OBJECTIVE

The objective of this study was to investigate whether reported mould or dampness exposure in early life is associated with the development of allergic disorders in children from eight European birth cohorts.

METHODS

We analysed data from 31 742 children from eight ongoing European birth cohorts. Exposure to mould and allergic health outcomes were assessed by parental questionnaires at different time points. Meta-analyses with fixed- and random-effect models were applied. The number of the studies included in each analysis varied based on the outcome data available for each cohort.

RESULTS

Exposure to visible mould and/or dampness during first 2 years of life was associated with an increased risk of developing asthma: there was a significant association with early asthma symptoms in meta-analyses of four cohorts [0-2 years: adjusted odds ratios (aOR), 1.39 (95% CI, 1.05-1.84)] and with asthma later in childhood in six cohorts [6-8 years: aOR, 1.09 (95% CI, 0.90-1.32) and 3-10 years: aOR, 1.10 (95% CI, 0.90-1.34)]. A statistically significant association was observed in six cohorts with symptoms of allergic rhinitis at school age [6-8 years: aOR, 1.12 (1.02-1.23)] and at any time point between 3 and 10 years [aOR, 1.18 (1.09-1.28)].

CONCLUSION

These findings suggest that a mouldy home environment in early life is associated with an increased risk of asthma particularly in young children and allergic rhinitis symptoms in school-age children.

Association between attendance of day care centres and increased prevalence of eczema in the German birth cohort study LISAplus

BACKGROUND

Day care centre attendance is much more common in East than in West Germany. Although there is evidence that early day care might be protective against atopic diseases, several studies have shown a higher prevalence of childhood eczema in East Germany compared to West Germany.

OBJECTIVES

To compare prevalence and cumulative incidence of eczema in a birth cohort study in East and West Germany and to identify risk factors that are associated with eczema, which might explain regional differences.

METHODS

We used data from the ongoing population-based birth cohort study Influence of Life-style factors on the development of the Immune System and Allergies in East and West Germany Plus the influence of traffic emissions and genetics. In 1997, 3097 children from study areas in East and West Germany were recruited. Cumulative incidence and 1-year prevalences of eczema up to the age of 6 years were determined from yearly questionnaires. Cox regression and generalized estimating equations/logistic regression were used to quantify regional differences and to identify risk factors that might explain them.

RESULTS

Prevalence and incidence of eczema were higher in children living in East Germany than those living in West Germany. We identified 11 risk factors that showed significant regional differences. From these factors, only 'day care attendance during the first 2 years of life' was significantly associated with eczema (odds ratio 1.56, 95% confidence interval CI 1.31-1.86). The regional differences in eczema could be explained by differences in early day care utilization.

CONCLUSION

Day care centre attendance is associated with an increased prevalence and incidence of eczema. Regional differences in eczema prevalence could be explained by regional differences in utilization of early day care.

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.

Genetic and environmental risk factors for childhood eczema development and allergic sensitization in the CCAAPS cohort

Eczema is very common and increasing in prevalence. Prospective studies investigating environmental and genetic risk factors for eczema in a birth cohort are lacking. We evaluated risk factors that may promote development of childhood eczema in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS) birth cohort (n=762) of infants with at least one atopic parent. Objective environmental exposure data were available for each participant. At annual physical examinations, children underwent skin prick tests (SPTs), eczema was diagnosed by a clinician, and DNA was collected. Among Caucasian children, 39% developed eczema by age 3. Children with a pet dog were significantly less likely to have eczema at age one (odds ratio (OR)=0.62, 95% confidence interval (CI): 0.40-0.97) or at both ages 2 and 3 (OR=0.54, 95% CI: 0.30-0.97). This finding was most significant among children carrying the CD14-159C/T CC genotype. Carriers of the CD14-159C/T and IL4Ralpha I75V single-nucleotide polymorphisms (SNPs) had an increased risk of eczema at both ages 2 and 3 (OR=3.44, 95% CI: 1.56-7.57), especially among children who were SPT+. These results provide new insights into the pathogenesis of eczema in high-risk children and support a protective role for early exposure to dog, especially among those carrying the CD14-159C/T SNP. The results also demonstrate a susceptibility effect of the combination of CD14 and IL4Ralpha SNPs with eczema.

Associations between cat keeping, allergen exposure, allergic sensitization and atopic diseases: results from the Children of Lübeck Allergy and Environment Study (KLAUS)

The role of cat keeping on the promotion of allergies is discussed controversially. We investigated the associations between cat keeping, allergen exposure, allergic sensitization and atopic diseases in pre-school children. A total of 606 children (5- to 6-yr old) were studied in the course of the mandatory school entrance examination. Information on doctor diagnosed asthma and allergic rhinitis, pet keeping and confounders was obtained by questionnaire. The prevalence of atopic eczema was determined by dermatological examination, allergic sensitization was assessed by skin prick test, and the allergen exposure to cat allergen Fel d 1 was measured by a commercial wipe test. Cats were present in 16% of the households and results of the exposure categories (0-III) on cat allergen were 47.2%, 25.5%, 24.3% and 3.0% respectively. The prevalence of cat keeping increased significantly with exposure categories from 0.5% to 61.5% (p(trend) < 0.001). Children (6.3%) were sensitized to cat allergen and sensitization rates increased also significantly with exposure categories from 3.0% to 15.4% (p(trend) < 0.001). Children (9.3%) were diagnosed with atopic eczema and a positive history of asthma/rhinitis was given in 3.6% and 3.9% respectively. Sensitization to cat was associated with atopic eczema (23.3% vs. 7.4%; OR(adj.)= 3.8, CI: 1.4-10.8), asthma (12.5% vs. 3.7%; OR(adj.)= 4.9, CI: 1.1-21.2), allergic rhinitis (6.9% vs. 2.7%; OR(adj.)= 3.1, CI: 0.7-15.2) and any atopic disease (43.5% vs. 16.3%; OR(adj.)= 3.8, CI: 1.5-9.5). The data suggest a promoting effect of cat keeping for atopic diseases.

The prevalence, characteristics of and risk factors for eczema in Belgian schoolchildren

Childhood eczema is common in infants, but its nature and extent during later childhood remains unclear. In this cross-sectional study we examined the prevalence and characteristics of eczema in an unbiased community population of 2,021 Belgian schoolchildren, aged 3.4 to 14.8 years with skin prick testing and parental questionnaires. Our study identified an eczema prevalence of 23.3% and a considerable allergic comorbidity, mainly in sensitized children. The reported prevalence of eczema in infancy was 18.5% and for current eczema 11.6%. The overall sensitization rate (33.2%) as well as sensitization rates for the individual allergens were significantly higher in children with "eczema ever." Sensitization to Dermatophagoides pteronyssinus (19.6%), mixed grass pollen (15.1%), and cat (9.1%) were most common. Until the age of 6 years, boys with eczema were significantly more sensitized than girls (p = 0.007). Children with both eczema in infancy and current eczema show a tendency to be more sensitized than children with eczema in infancy only or current eczema only, but significance was only noted for a few individual allergens. Analysis of factors associated with eczema revealed a predominantly atopic profile characterized by family or personal history of allergy. Breastfeeding and environmental factors seemed to assume little relevance except for a protective effect of prematurity and having a dog at birth.

Allergen tolerance versus the allergic march: the hygiene hypothesis revisited

In addition to genetics, several environmental variables appear to impact allergic risk. Meta-analyses of epidemiologic studies presented in this article demonstrate a correlation between specific ambient exposures (eg, livestock, pets, endotoxin, and unpasteurized milk ingestion) and reduced allergic risk during childhood. Additional laboratory investigations discussed in this review characterized the intrinsic immunostimulatory activities of living environments. Considered together, results of these investigations suggest a novel paradigm by which early-life home exposures to microbial products and other allergen-nonspecific immunostimulants modify allergic 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).

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.

Prenatal exposure to household pets influences fetal immunoglobulin E production

BACKGROUND

Early life pet exposure may protect against allergic sensitization during childhood. Few studies have evaluated the effect of prenatal pet exposure on potential neonatal markers of allergic risk.

OBJECTIVE

The aim of this study was to investigate whether maternal exposure to pets affects cord blood IgE levels in a population-based, general risk, ethnically mixed birth cohort.

METHODS

Pet keeping during pregnancy was ascertained from women residing in a defined area of Wayne County Michigan and recruited from five staff model obstetric clinics. Maternal venous blood was analysed for total and allergen-specific IgE along with cord blood total IgE from 1049 infants.

RESULTS

Compared with infants from households with no cats or dogs kept indoors during pregnancy, infants whose homes had either cats or dogs had significantly reduced mean cord IgE levels [0.34 IU/mL (95% CI 0.30-0.38) vs. 0.24 IU/mL (0.20-0.27), P=0.025]. Similar effects were apparent in cat-only households [0.21 IU/mL (0.16-0.27), P=0.020] and dog-only households [0.24 IU/mL (0.19-0.29), P=0.045]. There was no effect on results when excluding mothers who reported avoiding pets due to allergy-related concerns.

CONCLUSION

Mothers with either cats or dogs in their home during pregnancy deliver children with lower cord blood IgE levels compared with mothers who do not live with these pets, supporting the hypothesis that pet exposure influences immune development in a manner that is protective for atopy and is operant even before birth.

Environmental factors and allergic disorders

Despite numerous studies on possible associations between environmental exposure and allergic disorders, any conclusions made remain a matter of controversy. We conducted a review of evidence in relation to environmental and nutritional determinants and wheeze, asthma, atopic dermatitis, and allergic rhinitis. Identified were 263 articles for analysis after consideration of 1093 papers that were published since 2000 and selected by electronic search of the PubMed database using keywords relevant to epidemiological studies. Most were cross-sectional and case-control studies. Several prospective cohort studies revealed inconsistent associations between various environmental factors and the risk of any allergic disorder. Therefore, the evidence was inadequate to infer the presence or absence of a causal relationship between various environmental exposures and allergic diseases. However, evidence is suggestive of positive associations of allergies with heredity. Because almost all the studies were performed in Western countries, the application of these findings to people in other countries, including Japan, may not be appropriate. Further epidemiological information gained from population-based prospective cohort studies, in particular among Japanese together with other Asians, is needed to assess causal relationships between various environmental factors and allergic diseases.

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.

Home environment and suspected atopic eczema in Japanese infants: the Osaka Maternal and Child Health Study

Atopic eczema is most commonly diagnosed in children under the age of 5 yr. Environmental factors during pregnancy or in early life may confer risk for childhood atopic eczema. The present prospective study examined the relationship of the perinatal home environment and the risk of suspected atopic eczema among Japanese infants under the age of 1. Study subjects were 865 parent-child pairs. The term 'suspected atopic eczema' was used to define an outcome based on our questionnaire at 2-9 months postpartum. Adjustment was made for maternal age, gestation, family income, maternal and paternal education, maternal and paternal history of asthma, atopic eczema, and allergic rhinitis, time of delivery before the second survey, baby's older siblings, baby's sex, and baby's birth weight. A high mite allergen level from maternal bedclothes and mold in the kitchen during pregnancy were significantly associated with an increased risk of suspected atopic eczema. Frequent vacuuming practices during pregnancy and giving the infant a bath or shower at least once a day were significantly inversely related to the risk of suspected atopic eczema. Maternal smoking, maternal use of a synthetic duvet and pillow, carpet use in the living room and maternal bedroom, indoor domestic pets, no ducted heating appliance, and gas use for cooking during pregnancy and household smoking in the same room as the infant, infant's synthetic duvet, carpet use in the infant's room, or vacuuming the infant's room were not related to the risk of suspected atopic eczema. High house dust mite allergen levels and mold in the kitchen during pregnancy may increase the risk of infantile atopic eczema, whereas frequent vacuuming practices during pregnancy and giving the infant a bath or shower at least once a day may protect against infantile atopic eczema.

[Risk factors for atopic dermatitis and familial prevalence in Spain (ELIHO study)]

INTRODUCTION

Atopic dermatitis (AD) is a cutaneous disease of unknown etiology. It shows a clear genetic predisposition with probable environmental modulation. This study evaluated risk factors associated with diagnosis and flares of AD in Spanish children.

PATIENTS AND METHODS

We performed an observational, multicenter, retrospective case-control study that included 4243 children aged less than 14 years old with AD and 978 controls matched for age and sex. Family history of disease and environmental variables were collected in both groups and clinical history of AD was recorded in the case group.

RESULTS

Significant risk factors for AD were: a family history of the disease and concomitant cutaneous infections. The prevalence of AD in first degree relatives was 39 % and that in second degree relatives was 19 % (higher in maternal than paternal lines). The mean age of children with AD was 4.2 (SD 3.4) years and the mean age at diagnosis was 1.5 (SD 2.2) years, with a mean of 2.9 (SD 2.6) flares during the previous year. Cold weather (Cantabrian and Continental Iberian Peninsula areas) was related to a greater number of flares. Children with AD had a greater number of concomitant cutaneous diseases and infections than children in the control group.

CONCLUSIONS

AD is mainly a genetic disease, with climatic factors involved in severity modulation, and with important immunological alterations. In contrast, this study found no domestic environmental factors that were associated with disease onset.

Environmental and dietary risk factors for infantile atopic eczema among a Slovak birth cohort

Infantile atopic eczema (AE) is a risk marker for future asthma. This study assesses the contribution of modifiable exposures to infantile AE. If modifiable exposures contribute substantially to infantile AE, its prevention might be a sensible approach to asthma prevention. Pregnant women (n = 1978) were systematically recruited from maternity hospitals of the Slovak Republic; their birthed cohort of 1990 children were prospectively followed for 1 yr. Children's exposures to selected environmental and dietary factors were assessed via maternal questionnaires administered at delivery and 1 yr of age. A child was considered to have AE, based on physical examination (SCORAD index >2) or mother's report of a previous physician diagnosis. Multivariate logistic regression was used to calculate adjusted odds ratios and percent total regression scores (TRS) for each variable. At 1 yr of age 1326 (67%) of the children remained in the cohort and 207 (15.6%) developed AE. Various modifiable environmental and dietary exposures increased the likelihood of AE (ownership of cats; consumption of infant formula, eggs, and fish) while others decreased the likelihood of AE (ownership of livestock; exclusive breast feeding for > or =4 months). Overall, modifiable exposures contributed less to the TRS than did non-modifiable exposures (38% vs. 62%, respectively). The modifiable exposure category that contributed most to the TRS was infant feeding practices (27.5% TRS). Modifiable exposures -- especially those related to infant feeding practices -- significantly contribute to infantile AE, although modifiable factors contribute less overall than do non-modifiable exposures.

Current cat ownership may be associated with the lower prevalence of atopic dermatitis, allergic rhinitis, and Japanese cedar pollinosis in schoolchildren in Himeji, Japan

The aim of the study was to clarify the relationship between current pet ownership, passive smoking, and allergic diseases among the Japanese children. From 1995 to 2001, we distributed the Japanese edition of the questionnaire of the American Thoracic Society and the Division of Lung Diseases (ATS-DLD) to survey allergic diseases among 35,552 6-yr-old children at primary school in the city of Himeji, Japan. We analyzed the data by multiple logistic regression and calculated adjusted odds ratios for environmental factors, including passive smoking and pet (dog and/or cat) ownership. There were no significant relationships between the prevalence of asthma and current pet ownership and passive smoking. However, current cat ownership was related to a significantly lower prevalence of atopic dermatitis [adjusted odds ratio (aOR) 0.79, 95% confidence interval (CI) 0.67-0.93], allergic rhinitis (aOR: 0.71, 95% CI 0.57-0.89) and Japanese cedar pollinosis (aOR 0.57, 95% CI 0.44-0.75). Strikingly, passive smoking was also related to a significantly lower prevalence of allergic rhinitis (aOR 0.83, 95% CI 0.77-0.89) and Japanese cedar pollinosis (aOR 0.81, 95% CI 0.74-0.88). Current cat ownership was associated with a lower prevalence of atopic dermatitis, allergic rhinitis, and Japanese cedar pollinosis. In addition, passive smoking was also associated with a lower prevalence of allergic rhinitis and Japanese cedar pollinosis.

Atopic dermatitis and the 'hygiene hypothesis': too clean to be true?

BACKGROUND

The so-called 'hygiene hypothesis' postulates an inverse relationship between atopic dermatitis (AD) and an environment that leads to increased pathogen exposure.

OBJECTIVES

We sought to systematically identify, summarize and critically appraise: (i) the epidemiological evidence to suggest that environmental exposures that lead to an increase in microbial burden reduce the risk of AD; (ii) whether any specific infections have been shown to reduce AD risk; (iii) whether there is a link between immunizations, use of antibiotics and AD risk; and (iv) to comment on the new therapeutic approaches in AD that have evolved out of the 'hygiene hypothesis'.

METHODS

We searched Medline from 1966 until August 2004 to identify relevant studies for inclusion. Differences in study design and populations did not allow formal meta-analysis. Studies were therefore described qualitatively.

RESULTS

We identified 64 studies that were relevant to our review, 27 (42%) of which were of prospective design. There was prospective evidence to support an inverse relationship between AD and endotoxins, early day care and animal exposure. Two well-designed cohort studies have found a positive association between infections in early life and AD, and measles vaccination and AD. Antibiotic use was consistently associated with an increase in AD risk even into the antenatal period, although a few studies did not reach conventional statistical significance. A few small randomized controlled trials have suggested that probiotics can reduce AD severity and that probiotics may also be able to prevent AD to some degree.

CONCLUSIONS

Although population-based studies have suggested a consistent inverse relationship between AD and increasing family size, this does not seem to be explained by a straightforward increased exposure to a single environmental pathogen. The effect seen with early day care, endotoxin and animal exposure may be due to a nonpathogenic microbial stimulus of a chronic or recurrent nature. This would also explain the risk increase associated with antibiotic use. Caution should prevail in the prescribing of antibiotics early in life, especially in children with a family history of AD. Larger well-designed pragmatic trials on probiotics and the prevention and treatment of AD are now needed to inform whether such interventions should be used in routine clinical practice.

Exposure to pets, and the association with hay fever, asthma, and atopic sensitization in rural children

BACKGROUND

An increasing number of studies report pet exposure to be associated with lower risk of asthma and allergies. This 'protective pet effect' has been suggested to result from a modified T-helper (Th)2-cell response, or because of increased microbial load in homes where pets are kept. We examined the associations between pet contact and the occurrence of asthma and allergies in children of the rural Allergy and Endotoxin (ALEX) population, taking farm animal contact, endotoxin and cat allergen levels in mattress dust into account.

METHODS

Information about contact with pets and farm animals, asthma and allergy were collected for 812 children by a standardized parents' questionnaire and an interview. Mattress dust endotoxin and cat allergen levels as well as specific IgE and IgG4 antibodies to Fel d1 were determined.

RESULTS

Current contact with dogs was inversely associated with diagnosed hay fever (OR 0.26, 95% CI 0.11-0.57), diagnosed asthma (OR 0.29, 95% CI 0.12-0.71), sensitization to cat allergen (OR 0.48, 95% CI 0.23-0.99) and to grass pollen (OR 0.55, 95% CI 0.33-0.94), but not with increased IgG4 levels. Early and current contact with cats were associated with reduced risk of wheezing (OR 0.48, 95% CI 0.23-1.00, and OR 0.49, 95% CI 0.26-0.92, respectively) and grass pollen sensitization. Adjustment for farm animal contact but not for endotoxin and cat allergen exposure attenuated these associations and the effect of pet was stronger among farmers' children.

CONCLUSION

Although pet exposure was very frequent in this rural population, the inverse relation between current dog contact, asthma and allergy was mostly explained by simultaneously occurring exposure to stable animals or was restricted to farm children. In addition, a subtle form of pet avoidance may contribute to the protective effect of pet.

Does exposure to dogs and cats in the first year of life influence the development of allergic sensitization?

PURPOSE OF REVIEW

The goal of the review is to place studies published after 1 June 2002, concerning the relationship between early life exposure to cats and dogs and the later development of allergy, within the context of the effects of other environmental exposures on allergic disease.

RECENT FINDINGS

Most of the recent studies have shown that exposure to cats and dogs early in infancy reduces the prevalence of allergic sensitization or allergic disease later in childhood. While this general trend is relatively consistent, there are differences in specific findings between studies, such as the effect of parental allergies. Other studies suggest that the association between cat and dog exposure and a lower risk of allergy is due to either differences in other environmental exposures or to genetic differences between exposed and non-exposed children. It is impossible to directly compare the results from all of these studies since there are often important differences in racial/ethnic backgrounds of the children, climate, housing conditions, and the family and social customs of those enrolled in different studies.

SUMMARY

The risk of a child developing any form of allergy appears to depend upon many factors including a child's genetic constitution, early environmental exposure to allergens and to other agents which interact with the immune system, and to allergen exposure later in life. It appears that exposure to something that is increased in homes with cats or dogs reduces the risk of allergic sensitization.

Development of atopy and wheezing symptoms in relation to heredity and early pet keeping in a Swedish birth cohort

The role of pet keeping during infancy for the development of allergy and asthma is still controversial. The objective of this population-based birth cohort study was to assess the development of atopy and different wheezing phenotypes during the first 4 yr of life in relation to heredity and early pet keeping. The cohort comprised all 1228 infants living in a Swedish county who were born over a 1-yr period. The parents replied to repeated questionnaires and 817 of the children were skin prick tested both at 1 and 4 yr. Cat keeping during the first year of life was associated with an increased risk of a positive skin prick test to cat at 1 yr of age [odds ratio (OR) 2.2, 95% confidence interval (CI) 0.9-5.6], but neither with sensitivity nor clinical symptoms of allergy at 4 yr. Dog keeping during the first year of life was associated with an increased risk of early-onset transient wheezing, but only in children with parental asthma (adjusted OR 4.3, 95% CI 1.5-12.1). In contrast, early dog keeping had an inverse association with sensitivity to pollen allergen at 4 yr (adjusted OR 0.3, 95% CI 0.1-0.9) and late-onset wheezing (adjusted OR 0.4, 95% CI 0.2-1.0). Thus, pet keeping during the first year of life was not associated with an increased risk of atopy at 4 yr, although a positive SPT to cat was more common at 1 yr. Our findings may even suggest that dog keeping during the first year of life might provide some protection from pollen allergy and late-onset wheezing and increase the risk of early-onset transient wheezing in children with heredity for asthma.

Endotoxin exposure and eczema in the first year of life

OBJECTIVE

Exposure to endotoxin in early life has been proposed as a factor that may protect against the development of allergic diseases such as eczema. The objective of this study was to examine the relation between endotoxin exposure in early life and eczema in the first year of life in children with parental history of asthma or allergies.

METHODS

This study used a prospective birth cohort study of 498 children who had a history of allergy or asthma in at least 1 parent and lived in metropolitan Boston. A subset of 401 living rooms had house dust samples adequate for analysis of endotoxin.

RESULTS

In multivariate analyses adjusting for gender, income, and season of birth, endotoxin levels in the living room at 2 to 3 months of age was inversely associated with physician- or nurse-diagnosed eczema in the first year of life (odds ratio [OR] for each quartile increment: 0.76; 95% confidence interval [CI]: 0.61-0.96). Exposure to a dog in the home at age 2 to 3 months was also inversely associated with eczema in the first year of life, but the CI widened when endotoxin was included in the multivariate model (OR: 0.54; 95% CI: 0.27-1.09). Other variables associated with eczema in the first year of life included paternal history of eczema (OR: 1.91; 95% CI: 1.03-3.55) and maternal specific immunoglobulin E positivity to > or =1 allergen (OR: 1.61; 95% CI: 1.01-2.56).

CONCLUSIONS

Among children with parental history of asthma or allergies, exposure to high levels of endotoxin in early life may be protective against eczema in the first year of life. In these children, paternal history of eczema and maternal sensitization to at least 1 allergen are associated with an increased risk of eczema in the first year of life.

Effect of breast-feeding on the development of atopic dermatitis during the first 3 years of life--results from the GINI-birth cohort study

OBJECTIVE

To investigate if exclusive breast-feeding for 4 months is associated with atopic dermatitis during the first 3 years of life.

STUDY DESIGN

Data on 3903 children were taken from yearly parental-administered questionnaires from a birth cohort study in Germany (recruited 1995-1998) comprised of a noninterventional (NI) and an interventional (I) subgroup. Outcomes were physician-diagnosed atopic dermatitis (AD) and itchy rash. Multiple logistic regression was performed for the entire cohort and stratified by family history of allergy and by study group adjusting for a fixed set of risk factors for allergies.

RESULTS

Exclusive breast-feeding (52 % of children) was not associated with higher risk for AD either in the entire cohort (OR(adj,) 0.95; 95% CI, 0.79-1.14) or if stratified by family history of AD. In the I subgroup, but not in the NI subgroup, exclusive breast-feeding showed a significant protective effect on AD if compared with conventional cow's milk formula (OR(adj), 0.64; 95% CI, 0.45-0.90).

CONCLUSION

These findings do not support the hypothesis that exclusive breast-feeding is a risk factor for development of atopic dermatitis but is protective if compared with conventional cow's milk. Observational studies might not be able to effectively control for selection bias and reverse causation.