Dog Ownership at Three Months of Age Is Associated With Protection Against Food Allergy

Abstract

To investigate how environmental factors, specifically pet ownership, during infancy were associated with food allergy.The study consisted of 1303 3-month-old, healthy, exclusively breastfed infants from the general population of England and Wales. The study was done within the Inquiring About Tolerance study, an intervention study assessing the utility of early introduction of common allergens into diet, using the same group of infants.This prospective cohort study was planned as part of the Inquiring About Tolerance Study. Surveys were used at enrollment and monthly to determine environmental exposures in the study population. Family history of atopy, mode of childbirth, day care, antibiotic use, and pet ownership were included in the surveys. Specific immunoglobulin E assay and skin prick test (SPT) for cow’s milk, egg white, cod, peanut, sesame, and wheat were performed at the 3-, 12-, and 36-month visits to evaluate food sensitization in a double-blind placebo-controlled setting. Similarly, SPTs for house dust mites, cat, dog, grass, and tree pollen were performed at 12 and 36 months to evaluate aeroallergen sensitization. Infants were also assessed for atopic dermatitis and skin barrier function. Logistic regression analyses were then applied to assess the exposure variables in a dose-dependent manner (number of pets, access of pets of living spaces).Sixty-eight infants (6.1%, 68 out of 1124) were diagnosed with food allergy during the course of the study. Of those diagnosed, there was an increased association with atopy at the beginning of the study (crude odds ratio [cOR]: 5.74, P < .001), impaired skin barrier (cOR: 5.62, P < .001), and family history of allergy. Cohabitation with dogs was a protective factor against developing food allergy, as evident by a 90% odds reduction (adjusted odds ratio [aOR]: 0.10, P = .02). In fact, a dose-dependent response was seen in which more dogs and more access to living areas was associated with more protection (aOR: 0.11, P = .03). In those living with 2 dogs, there were no study participants who developed allergy. Dog ownership was also associated with decreased food SPT sensitization at 12 months (aOR: 0.17, P < .01) and 36 months (aOR: 0.35, P = .05), decreased aeroallergen sensitization at 36 months (aOR: 0.51, P = .05), and reduction in house dust mite sensitization (aOR: 0.34, P = .02).In the results of the study, it is suggested that cohabitation with dogs may prevent the development of food allergy in infants. The number of dogs present and their degree of access to the home were associated with a dose-dependent response. Additionally, dogs were found to be associated with decreased aeroallergen and house dust mite sensitization.The authors suggest that owning dogs and allowing dogs more access in the household protects against food and environmental allergies. Although efforts were made to adjust for confounding factors, it is difficult to adjust for all possible confounding environmental factors that may be impacting food allergy and atopy development. For example, could dog ownership be associated with increased time outdoors, allowing more sunlight exposure (vitamin D)? Greater understanding of the impacts of modifiable risk factors on allergy will allow improved counseling to families asking questions about whether lifestyle modifications can be beneficial.