PURPOSE OF THE STUDY.
To investigate the longitudinal effect of dog exposure on the risk of atopic dermatitis (AD) in children during the first 3 years of life. The study also evaluated the relationship between parental atopic disease, number of dogs, and cluster of differentiation 14 or filaggrin mutation genotypes on the development of AD.
The Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) are ongoing prospective clinical birth cohort studies. Data from 411 children born to mothers with asthma (COPSAC2000) and 700 unselected children (COPSAC2010) were analyzed.
AD was diagnosed according to the Hanifin and Rajka criteria. Exposure to dogs was determined by interviews during clinical visits and was defined as a dog living in the home at birth. The number of dogs was divided into the following 3 groups: no dog, 1 dog, or ≥2 dogs. Parental atopic history was determined by self-report of physician-diagnosed asthma, eczema, or allergic rhinitis. ImmunoCAP and skin prick testing of selected inhalant and food allergens was measured at 6 and 18 months.
In the COPSAC2000 and COPSAC2010 cohorts, children who had domestic dog exposure had a significantly lower risk of AD (adjusted hazard ratio [aHR] = 0.46 [95% confidence interval (CI) 0.25–0.87], P = .02; and aHR = 0.58 [95% CI 0.36–0.93], P = .03, respectively). In the unselected COPSAC2010 cohort, the protective effect was only seen in children born to mothers with atopic disease (aHR = 0.39 [95% CI 0.19–0.82], P = .01). Paternal atopic status did not impact the risk of AD. The risk of AD decreased in a dose-dependent manner with increasing number of dogs (aHR = 0.58 [95% CI 0.38–0.89], P = .01) in the COPSAC2010 cohort. Dog exposure did not impact the development of AD in children with filaggrin mutations. No significant interaction was found between domestic dog exposure and the cluster of differentiation 14 T/T genotype.
Domestic dog exposure at birth significantly reduced the risk of AD in children born to mothers with a history of atopic disease. This effect was dose dependent.
Although researchers in some previous studies have suggested that domestic dog exposure might protect against the development of allergic disease, the effects of neonatal dog exposure on the risk of AD is unresolved. The authors of this study help to clarify this question and further emphasize the importance of the perinatal environment on the risk of atopic disease. Further studies are needed to elucidate the mechanisms underlying these effects, with prime hypotheses focused on the microbiome of the mother and infant.
- Copyright © 2017 by the American Academy of Pediatrics