Influence of household pet ownership and filaggrin loss-of-function mutations on eczema prevalence in children: A birth cohort study

Background: The association between pet exposure in infancy, early childhood eczema, and FLG mutations remains unclear. Methods: This was a birth cohort study performed in Tokyo, Japan. The primary outcome was current eczema based on questionnaire responses collected repeatedly from birth to 5 years of age. Generalized estimating equations and generalized linear modeling were used to evaluate the association. Results: Data from 1448 participants were used for analyses. Household dog ownership during gestation, early infancy, and 18 months of age significantly reduced the risk of current eczema. Household cat ownership also reduced the risk of current eczema, albeit without statistical significance. The combined evaluation of children from households with pets, be it cats, dogs or both, the risk of current eczema at 1–5 years of age was lower in those with household pet exposure ownership during gestation (RR = 0.59, 95 % CI 0.45–0.77) and at 6 months (RR = 0.49, 95 % CI 0.36–0.68). , Reduced risks of eczema were also observed at 2–5 (RR = 0.52, 95 % CI 0.37–0.73) and 3–5 years of age (RR = 0.50 95 % CI 0.35–0.74) when the respective household pet ownership were evaluated at 18 months and 3 years of age. These protective associations of reduced risk of eczema were only observed in children without FLG mutations. Conclusions: Household dog and pet (dog, cat, or both) ownership was protective against early childhood eczema in a birth cohort dataset. This protective association was observed only in children without FLG mutations, which should be confirmed in studies with larger cohorts.