Study Kicks Up Dust Over Mites' Role in Asthma

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Study Kicks Up Dust Over Mites' Role in Asthma

Tue Mar 5,11:55 PM ET

By Adam Marcus

HealthScoutNews Reporter

TUESDAY, March 5 (HealthScoutNews) -- Dust mites have long been

considered a leading source of allergies and asthma in the home.

However, a surprising new study found the more the people were exposed

to the irritants, the less likely they were to have asthma.

" I think our study is probably going to stir up some feathers, " says Dr.

Darryl Zeldin, study author and a lung specialist at the National

Institute of Environmental Health Sciences. The results were presented

today at a meeting in New York of the American Academy of Allergy Asthma

and Immunology.

The study by government and academic researchers compared mite levels

and asthma rates in 831 homes nationwide -- the first such look of its

kind. A group led by Arbes, of the National Institute of

Environmental Health Sciences, tested bedding for the presence of two

key dust mite proteins: Der f 1 and Der p 1, both of which are known to

spark allergic reactions.

If these allergens were indeed asthma triggers, people exposed to more

mite proteins in their bedding would be expected to be at greater risk

of symptoms. However, the allergens and asthma were inversely related:

as mite burden rose, asthma rates fell.

Of the homes with bedding containing the highest levels of mite

allergens, 18.5 percent had at least one resident ever diagnosed with

asthma. That rate rose to 27.2 percent for homes with moderate exposure,

and to nearly 29 percent for homes with the lowest level of allergens in

bedding, the researchers say. In other words, the odds of a someone

heavily exposed to mite allergens having been diagnosed with asthma were

about 44 percent lower than if their exposure was low.

Zeldin says homes of asthmatics were no dirtier, on average, than those

of people without the breathing disorder. Nor were they more likely to

have pillow and bed covers and other protective measures against mites.

Arbes offers two explanations for the startling findings. Some unknown,

provocative allergens lurk in house dust -- and he and his colleagues

are now looking for possible offenders beside eight-legged, blind mites.

Similarly, mite proteins may interact with other known allergens, like

those from cockroaches.

Or, Arbes says, exposure to dust mite proteins may help the immune

system tolerate irritants in a way that reduces asthma and other

allergic reactions. This theory has received a boost with recent reports

that children who live with dogs and cats appear to gain protection from

asthma.

The bottom line, Arbes says, is that for now, the scientists are

puzzled: " At this point, we don't know why we're getting this result. "

What To Do

So, should you get rid of those pillow covers and ultra-fine vacuum

filters? " Absolutely not, " Arbes says. " We still think lowering

allergens [in the home] is a good thing. "

Washing bedding in hot or treated water, and wrapping mattresses and

pillows in protective covers can reduce exposure to dust-mite allergens

markedly.

For tips on how to reduce the dust mite population in your home, visit

the National Institute of Environmental Health Sciences

<http://www.niehs.nih.gov/airborne/prevent/mites.html> .

For more information on dust mite allergies, go to About.com

<http://About.com> or the American Academy of Allergy Asthma and

Immunology

<%20http://www.aaaai.org/patients/publicedmat/tips/indoorallergens.stm%20>

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