Bad News for Cats: Cat allergen hits all allergic people

For people who have asthma or respiratory problems that are triggered by cats, living with Fluffy is obviously a bad idea. Now, researchers have found evidence suggesting that people who know that they have other allergies may also want to avoid the furry felines.

HIGHLY IRRITATING. People allergic to things other than cats possibly should avoid the animals anyway because their presence can make people’s lungs more sensitive to a wide range of allergens. iStockphoto

Scientists who conducted a study across 14 European countries say that people allergic to irritants such as dust mites, mold, and grass had poorer lung function if they were around cats than if they lived felinefree.

“Cats are more of a problem than we thought,” says lead author Sue Chinn of Imperial College London.

The unexpected result emerged from a broad study of allergy and lung function. The researchers went into the homes of 1,884 randomly selected volunteers and tested mattress-dust samples for allergens from cats and dust mites. Volunteers were also tested to determine whether they were allergic to common triggers such as dust mites, cats, Cladosporium mold, and timber grass, a relative of Kentucky bluegrass.

Scientists tested participants for allergies by measuring their blood concentrations of antibodies of a type known as immunoglobulin E (IgE). An allergic reaction occurs when an IgE antibody binds to an otherwise harmless compound and spurs the immune system into action.

To assess how living amid differing amounts of triggers affected participants’ respiratory systems, the scientists had volunteers undergo a lung-function assessment that included a test of how strongly their lungs constricted in response to an irritant.

Surprisingly, Chinn says, people living around cats performed worse on the lung function test even if they weren’t specifically allergic to cats. By contrast, exposure to dust mites made no difference to the test results of people not allergic to the bugs.

The scientists had expected that people’s lungs would constrict only when exposed to the stimulants that trigger their allergies, as happens in people with asthma (SN: 11/27/04, p. 344).

Chinn cautions not to give away Fluffy just yet because “the study needs to be replicated before we start getting too excited.” The results appear in the July American Journal of Respiratory and Critical Care Medicine.

Dennis Ownby, a physician at the Medical College of Georgia in Augusta, notes that one of the more interesting findings of the study is that exposure to cats affected participants’ breathing more than exposure to house dust mites did.

“For many years, a tremendous amount of work was done on [the study of dust] mites in homes and the risk of asthma on the people living there,” he says. “This study now suggests that mites are not that important.”

The results don’t necessarily indicate a cause-and-effect relationship, Ownby says. “It’s possible that higher [sensitivities to] cat allergens are directly related to something else in the home and [that] we’re just not measuring the primary culprit.”

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