Early exposure to pets does not increase risk of allergies in children

Having a pet dog or cat in the house does not increase a child’s risk of becoming allergic to these animals. In fact, it may have a protective effect, according to a new study.

Researchers collected data on exposure to indoor dogs and cats through annual interviews with families of children enrolled in the Childhood Allergy Study from birth to age 6 years. At age 18, 566 study participants were interviewed and provided blood samples so that researchers could measure antibodies to dog and cat allergens.

Among young men but not young women, those whose families had an indoor dog in their first year of life were half as likely to be sensitized to dogs at age 18 compared with those who did not have an indoor dog in their first year. Both young men and women exposed to indoor cats during their first year of life had half the risk of being sensitized to cats at age 18 compared with those not exposed to an indoor cat.

The first year of life was the critical exposure period. Neither cumulative lifetime exposure to pets nor exposure at any other particular age was associated with later sensitization.

The finding “argues for the importance of the timing of the exposure with respect to early life immune development,” according to the researchers. This may explain why previous studies of pet exposure and allergies, which have not defined timing of animal exposure, have had mixed results.

Wegienka G, Johnson CC, Havstad S, Ownby DR, Nicholas C, Zoratti EM. Lifetime dog and cat exposure and dog- and cat-specific sensitization at age 18 years. Clin Exp Allergy. 2011;41(7):979-986.