It has previously been shown that early exposure to cats and dogs may have a protective effect for children prone to developing allergies. New research now shows that being exposed to secondhand smoke could negate that protective effect, according to a study presented at the 2004 Annual Meeting of the American Academy of Allergy, Asthma and Immunology (AAAAI)…

Dennis Ownby, MD, FAAAAI, from the Medical College of Georgia, and colleagues analyzed the relationship between exposure to cats and dogs during the first year of life and the risk of developing allergies at 6-7 years of age in 474 children. They also evaluated parental smoking habits during pregnancy.

Results from the study showed:

Children of nonsmoking parents were significantly less likely to develop allergies if they were exposed to 2 or more cats or dogs than children exposed to 1 or no pets.

Exposure to 2 or more cats or dogs did not alter the risk of developing allergies in children of smoking parents.

This study further supports the theory that exposure to pets early in life protects against the development of allergies. However, the protection is negated upon exposure to secondhand smoke.

Long-term secondhand pre- and postnatal tobacco smoke exposure increases the risk for the development of allergic sensitization and asthma during the first 10 years of life, according to a study presented at the 2004 AAAAI Annual Meeting in San Francisco.

Michael Kulig and colleagues from Charite University Medical Center in Berlin, Germany measured the long-term effects of tobacco smoke in 1,314 newborns through parental questionnaires and/or interviews. Four outcomes were considered: allergic sensitization to inhalant allergens, allergic rhinitis, wheezing and respiratory infections. Long-term effects of environmental tobacco smoke (ETS) were measured by generalized estimating equation models that were adjusted for education, birth weight, breast feeding, number of siblings and pets.

Results showed that ETS exposure increased with age. Eighteen percent of children had been exposed continuously by their mothers smoking and 40 per cent of children had never been exposed to their parents smoking. In children who have parents with allergies, combined in utero tobacco (IUT) and regular maternal ETS exposure significantly increased the risk for allergic sensitization and asthma.