Relationship of pet exposure and atopic dermatitis (AD) in the childhood allergy study (CAS)

We have reported that early-life pet ownership is protective for positive serum specific IgE and skin tests to inhalant allergens at age 6. We investigated whether the presence of household cats or dogs affects childhood AD incidence. We analyzed data from 474 participants in CAS, a prospective birth cohort who completed a study exam at age 6. AD was based on parental response to the question “Did a physician ever tell you your child had atopic dermatitis or eczema?” Pet exposure was categorized as no household cats or dogs, 1 pet and 2 or more pets. Using logistic regression, we assessed confounding and interaction for gender, parental history, birth order, parental smoking, dust mite exposure, fever and antibiotic use. 47% of the households had no pets, 36.5% had one and 16.5% had ≥2 cats or dogs. AD was reported in 59 (12.4%). Unadjusted analyses failed to show associations between pet ownership and physician diagnosed AD. The association between pet ownership and AD differed by parental smoking behavior. For children of smokers (n=142), the adjusted odds ratio (OR) between 1 pet and AD was 0.15 (95% confidence interval (CI) 0.02-1.35, p=0.17), and for ≥2 pets the OR=0.59 (CI 0.06-5.8, p=.73). For children of non-smokers (n=329), the OR for one pet and AD was 1.64 (CI 0.75-3.59, p=0.85) and for ≥2 pets 3.08 (CI 1.22-7.73, p=0.04). Pet ownership in the first year of life may increase risk of AD among children of non-smokers, emphasizing the need to consider multiple risk factors.