Exposure to Cats and Dogs, and Symptoms of Asthma, Rhinoconjunctivitis, and Eczema

Background: Associations between exposure to cats and dogs and respiratory and allergic outcomes in children have been reported in affluent countries, but little is known about such associations in less-affluent countries. Methods: The International Study of Asthma and Allergies in Childhood, phase 3 was carried out in children aged 6-7 years and adolescents aged 13-14 years across the world. Questions about cats and dogs in the home were included in an additional questionnaire. Using logistic regression, we investigated the association between such exposures and symptoms of asthma, rhinoconjunctivitis, and eczema. Adjustments were made for sex, region of the world, language, gross national income per capita, and 10 other covariates. Results: Among children (6-7 years of age), cat exposure in the first year of life was associated with current symptoms of asthma, wheeze, rhinoconjunctivitis, and eczema, especially in less-affluent countries. Among adolescents (13-14 years of age), we found a positive association between exposure to cats or dogs and symptom prevalence in more-affluent and less-affluent countries. The global multivariate odds ratios, for children with complete covariate data were 1.17 (95% confidence interval = 1.08-1.29) for current symptoms of asthma, 1.13 (1.05-1.23) for rhinoconjunctivitis, and 1.38 (1.26-1.52) for eczema. Smaller odds ratios were found for exposure to only dogs. Exposure to only cats was associated with eczema. Conclusion: Early-life exposure to cats is a risk factor for symptoms of asthma, rhinoconjunctivitis, and eczema in 6-to 7-year-old children, especially in less-affluent countries. Current exposure to cats and dogs combined, and only to dogs, is a risk factor for symptom reporting by 13-to 14-year-old adolescents worldwide.