Dog Ownership at 3 Months of Age is Associated With Protection Against Food Allergy

A secondary, ad hoc analysis evaluating the association between dog ownership and food allergy development was performed in The Inquiring About Tolerance (EAT) cohort.

The EAT study enrolled 1303 healthy and exclusively breastfed 3-month-old infants from the general population across England and Wales into a randomized trial investigating whether the early dietary introduction of six allergenic solids (egg, peanut, milk, wheat, cod and sesame) reduced the prevalence of food allergy diagnosed from 12–36 months of age.

At enrollment, pet ownership was reported by questionnaire and infants were examined for atopic dermatitis. Reactions to foods were reported on monthly questionnaires. Sensitization to foods and aeroallergens was elicited by skin prick and serum IgE testing at 3, 12 and 36 months. Food allergy status was determined by double-blind placebo-controlled oral food challenges (DBPC-OFC) between 1 and 3 years.

Food allergy was diagnosed in 6.1% (68/1124) of infants with complete data. After adjusting for familial atopic disease, maternal dog/cat sensitization and infant atopic dermatitis, living with dogs was associated with a 90% reduction in the odds of infants developing food allergy (OR 0.10, 95% CI 0.01–0.71, P = .02), with dose responses for owning an increasing number of dogs (OR 0.12, 95% CI 0.02–0.81, P = .03) and closer infant–dog cohabitation (OR 0.11, 95% CI 0.02–0.79, P = .03). There was no relationship between dog ownership and atopic dermatitis (P = .89), interaction between dog ownership and atopic dermatitis on the likelihood of developing food allergy (P = .78), or confounding by randomization group from the original study.

Dog ownership in infancy is inversely associated with food allergy development, after adjusting for infant atopic dermatitis and maternal sensitization.

This study demonstrates an inverse association between dog ownership and food allergy diagnosed by DBPC-OFC in a general-population cohort of breastfed infants. Study strengths include the prospective reporting of dog ownership and of conscious avoidance of dog ownership and the objective measurement of maternal dog sensitization, all of which help to avoid reverse causation bias from infants being at higher risk of food allergy if their parents avoid dogs because of their own allergies. The study is observational and cannot demonstrate causation, although it strongly contributes to the literature evaluating environmental exposure and childhood allergy associations.