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Brief Description:

Researchers at the National Institutes of Health have found that more than 50 percent of the current asthma cases in the country can be attributed to allergies, with about 30 percent of those cases attributed to cat allergies.

Transcript:

Schmalfeldt: Researchers at the National Institutes of Health have found that more than 50 percent of the current asthma cases in the country can be attributed to allergies, with about 30 percent of those cases attributed to cat allergies. Researchers at the National Institute of Environmental Health Sciences and the National Institute of Allergy and Infectious Diseases determined that 56.3 percent of asthma cases are attributed to atopy—a condition that results from gene-environment interactions. Dr. Darryl C. Zeldin, a senior investigator at the NIEHS, said that sensitivity to cat allergens appears to be a strong risk factor for asthma in this study, but that some research shows that exposure to cats, particularly in early life, may be a protective factor.

Zeldin: What we're looking at in our study is current exposure to allergens and current asthma symptoms. That said, there is certainly significant literature out there that suggests that early exposure to things like cats and dogs and farm animals is protective and it's thought that it leads to the development of a tolerance or to an immune system that's less likely to be allergic.

Schmalfeldt: A positive skin test reaction to cat allergens accounted for 29.3 percent of the asthma cases, followed by 21.1 percent for a fungus known as Alternaria and 20.9 percent for white oak. Dr. Zeldin said there are several implications to be drawn from the study.

Zeldin: First is that if one can somehow prevent the development of allergy to cat, Alternaria and white oak, then a significant number of asthma cases could potentially be prevented. The other way to look at the coin is although 50-plus percent of individuals have asthma that can be attributable to this allergy or atopy, that means that just under half of asthma cases have a non-allergic etiology. In other words, their asthma is not related to development of allergy. And I think that we and other scientists are trying to figure out what other things may be causing or exacerbating asthma in the indoor environment and I think there needs to be further research in this area.

Schmalfeldt: The study is available online in the Journal of Allergy and Clinical Immunology. From the National Institutes of Health, I'm Bill Schmalfeldt in Bethesda, Maryland.