Exposure to cat dander can impair lung function in people with asthma for up to 22 hours, according to a new study.

Cat allergen is a common irritant for many of the 15 million Americans with asthma. Often, it doesn't trigger an asthma attack directly, but contributes to inflammation of the small airways that, if left untreated, leads to severe asthma attacks later.

This extended inflammatory lung reaction often brings no detectable symptoms and is hard to catch using conventional lung-function tests. But researchers at the University of California-Los Angeles developed a new high-resolution computed tomography imaging technique that allows them to see the function of airways deep inside the lungs.

"We studied cat allergen because it's an extra-fine particle that is both airborne and capable of penetrating deep into the small airways," said Jared Allen, a researcher at UCLA's David Geffen School of Medicine and lead author of the study presented Tuesday before the annual meeting of the Radiological Society of North America in Chicago.

Allen's team did baseline tests on 10 people with known allergies to cats. After being exposed to cat allergens, the patients were studied for three days.

All of them showed significant and prolonged decrease in lung function well after any outward symptoms had faded.

By clinical measures, all the patients appeared to have recovered by 22 hours after exposure. But in the CT scans, they still "showed significant air trapping, suggesting that constriction and inflammation of the small airways remain long after initial exposure," Allen said.

The findings are particularly important in light of reports that childhood rates of allergy and asthma are rising, and that there is persistent exposure to pet allergens in homes and schools.

One recent national survey found that even though fewer than half of all American homes contain dogs or cats, 100 percent and 99.9 percent contain dog and cat allergens, respectively.

Allen said it's difficult to reach the smallest airways with conventional asthma inhalers and that the findings point to a need to develop new inhaler devices and drugs that can suppress inflammation deep in the lungs.

"Better understanding of the causes and complications of asthma, as afforded by this type of imaging, will lead to improved and targeted therapies for this disease," Allen said.

Seattlepi.com