Indoor pet exposure and the outcomes of total IgE and sensitization at age 18 years

Background: Early-life exposure to household pets has been shown to be protective against allergic sensitization in childhood. Objective: We sought to evaluate the association between earlylife pet exposure and allergic sensitization at age 18 years. Methods: Teenagers who had been enrolled in the Detroit Childhood Allergy Study birth cohort in 1987-1989 were contacted at age 18 years. Serum total and allergen-specific IgE levels to 7 common allergens (dust mite, cat, dog, ragweed, Timothy grass, Alternaria species, and peanut; atopy was defined as any specific IgE level >0.35 kU/L) were measured at age 18 years. Annual interview data from childhood were used to determine indoor dog and cat (≥50% of their time in the home) exposure during early life. Exposure was considered in various ways: first year, cumulative lifetime, and age groups, as well as multiple pets. Results: Dog or cat exposure in the first year of life was not associated with atopy (relative risk, 0.97; 95% CI, 0.83-1.12). Those living with pets in the first year and atopic at 18 years had lower total IgE levels. Neither cumulative exposure nor exposure at a particular age was strongly and consistently associated with either outcome. Although not statistically significant, there was a pattern of decreased odds of sensitization among those with 2 or more pets versus no pets in the first year of life. Conclusions: Early-life pet exposure can be associated with lower total IgE levels among atopic subjects but is not strongly associated with decreased likelihood of sensitization to common allergens at age 18 years.