Cat Allergen Triggers Longer Effects in Humans

Effects of cat allergen exposure last longer than previously thought.

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Researchers have developed a new high-resolution computed tomography technique which shows that cat allergens can impair lung function in people with asthma for up to 22 hours after exposure. The HRCT technique, unlike conventional pulmonary function tests which often can not detect prolonged inflammatory lung reaction, examines the function of small airways deep in the lungs to reveal the extent of impairment from cat allergen exposure.

The study evaluated cat allergens because they are extra-fine particles that are both airborne and capable of penetrating deep into the small airways of the lungs, says lead author Jared W. Allen, Ph.D., researcher at David Geffen School of Medicine at the University of California, Los Angeles. The study says exposure to cat allergens are very common and can contribute to disease. In many cases, the lung changes triggered by allergen exposure do not produce symptoms but contribute to persistent inflammation in the small airways that could lead to subsequent severe asthma attacks if left untreated.

For the study, the researchers used baseline pulmonary function tests and HRCT to measure lung function in 10 people with known allergy to cats. After being exposed to cat allergens, the patients were studied for three days. The results showed all 10 patients exhibited significant and prolonged decrease in lung function, even after outward symptoms had ceased.

Although patients appeared to have recovered from respiratory symptoms after 22 hours, HRCT still showed significant air trapping, suggesting that constriction and inflammation of the small airways remain long after initial exposure, says Dr. Allen.

A 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, says Dr. Allen. In addition, the quantitative image analysis used in this study may be one of the safest ways to evaluate the efficacy of these new [oral anti-inflammatory drugs] drugs  and aerosols [inhalers] in the treatment of asthma.

The study was presented Tuesday, Nov. 29 at the Radiological Society of North Americas annual meeting in Chicago.

Posted: Nov. 29, 2005, 4p.m. EST

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