Cat Allergy Linked to Asthma

More than half of asthma cases in the U.S. are linked to
allergies, with sensitivity to cats responsible for 29% of allergy-related
asthmas, according to new research from the National Institutes of Health.

Allergic sensitivity to cats, confirmed through skin testing, was associated
with a threefold increase in asthma risk in the study, conducted using data
from the nationally representative health survey, NHANES III.

Cat allergy was the strongest single predictor of asthma risk among the
common allergen exposures examined, but sensitivity to white oak and the common
outdoor fungus Alternaria were also independently associated with asthma
risk.

"This study confirms that the environment plays a major role in the
development of asthma," says Darryl C. Zeldin, MD, of the National
Institute of Environmental Health Sciences (NIEHS).

Asthma, Allergies, and Cats

Along with researchers from the National Institute of Allergy and Infectious
Diseases (NIAID), Zeldin and NIEHS colleagues examined skin test data for 10
common allergens from a nationally representative sample of 10,508 people
between the ages of 6 and 59.

The findings led the researchers to conclude that 56.3% of the asthma cases
in the U.S. are linked to allergies.

Each of the 10 allergens was initially found to be associated with an
increase in asthma risk, but after adjusting for other potential risk factors
only sensitivity to cats (29%), Alternaria (21%), and white oak (21%)
remained independent predictors of risk.

Other allergens tested included ragweed, dust mites, Russian thistle,
Bermuda grass, peanuts, perennial rye, and German cockroach.

While the study confirms an increase in asthma risk among people with
established cat allergies, it says little about the impact of specific
exposures to cats or the other asthma-related allergens identified.

The distinction is likely to be important to anyone who shares a home with a
feline.

The findings would seem to indicate that exposure to cats increases asthma
risk, but other studies have suggested that exposure early in life may actually
protect children from developing cat allergies in the first place.

Not All Asthma Cases Linked to Allergies

Zeldin tells WebMD that an as yet unpublished analysis of more recent NHANES
data should provide a better picture of exposure-associated risk.

"We are not telling people to get rid of their cats," Zeldin says.
"What we can say from this study is that people with documented cat
allergies have an increased risk for developing asthma."

He adds that people with such allergies should probably limit their exposure
to cats.

"That just makes sense," he says.

The new research also makes it clear that while a large number of asthma
cases in the U.S. are associated with allergies, many others -- roughly 45% --
are not.

"This study tells us that allergy is a major factor in asthma,"
Peter Gergen, MD, MPH, of the NIAID says in a news release. "But this study
also tells us that there are many people who get asthma who don't have
allergies. We need to do more research to understand what is causing asthma
that is not related to allergies."

The study appears in the Sept. 27 online edition of the Journal of
Allergy and Clinical Immunology.

By Salynn Boyles
Reviewed by Louise Chang
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