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Lullaby and Good Mite

Dust mites found in bedding in millions of homes, study says

TUESDAY, May 22 , 2001 (HealthDayNews) -- A major cause of your allergies may not be those blooms in your garden or that freshly cut grass, but the critters that live in your mattress, pillows, blankets and other bedding, a new study says.

And you're not alone. One-quarter of the homes surveyed in the First National Survey of Lead and Allergies in Housing had dust mite allergen levels in bedding high enough to trigger asthma and allergies.

"It's well established that mite allergen exposure is a major problem in the bed. But what was surprising is that 90 percent of the homes had detectable levels," says Dr. Darryl C. Zeldin, the study's lead author and head of the clinical studies section at the National Institute of Environmental Health Sciences (NIEHS). His findings were presented today at the 97th International Conference of the American Thoracic Society in San Francisco.

From their sampling, the researchers estimate that 23.2 million homes contain high levels of dust mite allergens. And Zeldin adds, "86 million homes in the U.S. have some level of bed mite allergens."

The all-but-invisible dust mite is a spider-like bug that takes up residence on flakes of human skin upon which it excretes allergen-containing protein from its digestive tract.

Researchers studied dust samples and measured the protein levels in 831 homes in 75 areas of the country, between l998 and l999.

Several factors increased the amount of allergens, says Zeldin. More mites are found in non-western regions of the United States. "They love warm, humid climates."

High levels of mites were also found in low-income households, in single family homes -- especially those built before 1978 -- and where the bedroom smelled of must or mildew.

"My guess is the major [factor] is the older homes have more problems with moisture and water sources, which mites thrive on," says Zeldin. And, with low-income households, it may be that "a lot of people don't have vacuums."

In addition to the mite allergens, the study also showed cockroach allergens were in 6 percent of the bedrooms. He says 17 percent of the homes studied reported roach problems last year, and "that is consistent when we look at the kitchen. Roaches don't live in beds very often" and are most often attracted by food debris.

"Knowing what factors are associated with the high levels will allow us to target intervention and prevention efforts," Zeldin adds.

"This is an important study because it provides a genuine cross-section of the population to give us some idea of the real distribution of allergen levels in houses across the country," says Dr. Thomas Platts-Mills, director of the Asthma and Allergic Diseases Center at the University of Virginia.

"Dust mite sensitization is the strongest risk factor worldwide for asthma," Platts-Mills adds. "It's important we recognize this when people do studies on methods of reducing exposure, and this study provides important background."

Zeldin says there are other studies underway. "We'll also try to associate the exposure with disease, look at the health status of the people, how often they are sick, what they have," and also look at cat and dog allergens, fungal allergens and those left behind by rodents.

The NIEHS and the Department of Housing and Urban Development sponsored the study.

What To Do

There are some things you can do, says Zeldin, to keep the tiny bugs at bay. "Put impermeable covers on your mattress, box spring and pillow, fully encasing them. They zip up, are tightly meshed and don't allow mite allergens to get out."

Combine that, says Zeldin, with regular weekly washing in hot water greater than 130°F, removable bed items such as comforters, blankets and sheets. Vacuum, or if possible, remove carpeting.

Also, control moisture with dehumidifiers, moisture-proof the foundation of your house, and clean up any food left lying around.

Find out more about household allergens from the National Institute of Environmental Health Sciences.

Learn what you can do to control indoor allergies from this Asthma Magazine article in the Sneeze Gazette.

Or read more HealthDay stories on household allergens here.

SOURCES: Interviews with Darryl C. Zeldin, M.D, head of clinical studies, National Institute of Environmental Health Sciences, and lead author; Thomas Platts-Mills, M.D., Ph.D., professor of medicine, and director, Asthma and Allergic Diseases Center, University of Virginia, Charlottesville, Va.
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