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Cleaning Is Mite-y Good

Allergy-causing dust mites fall victim to cheap, easy weapons -- soap, water, vacuum

FRIDAY, Aug. 10, 2001 (HealthDayNews) -- Sometimes, the simple things work best.

People with asthma or a dust allergy can quickly reduce the odds of an attack by going on the offensive in their bedrooms, says research released this week by the National Institute of Environmental Health Sciences.

"That's the single most-important site for exposure to indoor allergens, simply because that's where people spend most of their time," says lead researcher Dr. Darryl Zeldin, head of the agency's clinical studies section.

But not just people populate bedrooms. It's also a hideout for dust mites, microscopic organisms that live in household dust, along with animal dander, mold spores, tiny food particles and fabric fiber. Mites thrive in warm, humid environments and especially proliferate in bedroom trappings like carpeting, comforters, pillows and mattresses.

Like pollen, dust mites can prompt allergic reactions and asthma attacks, experts say.

But simple, cheap and widely available methods can reduce mite populations to levels most people can tolerate, Zeldin says.

First, put allergen-proof covers on your mattress, box springs and pillows, he says. Made of tightly woven fabric, the fully encasing covers keep the mites out, Zeldin says. Then, wash all your bed linens weekly in hot water.

As for carpeting, another favorite hangout for mites, vacuum frequently. And, if you can afford it, have your carpeting "dry" steam-cleaned periodically, the study suggests. This type of cleaning uses a small amount of hot, pressurized water or steam, without chemicals, according to various companies that make the equipment.

The hot cleaning seems to kill the mites, and the vacuuming removes them, the study says.

Some 20 million Americans are allergic to dust mites, says Maryanne Ellis, executive director of the Maryland-Greater Washington, D.C., chapter of the Allergy and Asthma Foundation of America.

"I have it; almost everybody has it, unfortunately," Ellis says.

But having a dust-mite problem "doesn't mean your house isn't clean," she says. "It's really the mites, not the dust, you see in your house that are the problem."

"But it's true that if you keep your home as clean as possible, it lessens the dust mite allergy," she says.

Zeldin and researchers from Harvard University and the University of Washington tested 39 homes in Seattle with high concentrations of dust mites to see if they could cut the dust mite population reasonably quickly. During the study, which spanned eight weeks between 1999 and 2000, the researchers collected dust from carpeting, bedding and upholstered furniture, Zeldin says.

"The levels started out quite high, anywhere from 50 to 100 micrograms of mite allergens per gram of dust," he says. "But we were able to get the levels down below 10 [micrograms of mites per gram of dust], probably as low as 7 or 8, by two weeks. And they stayed down at that level for eight weeks." Details appear in the August issue of the journal Environmental Health Perspectives.

"We think that 10 is a level below which you have reduced asthma symptoms and above which you have increased symptoms," Zeldin says.

But beyond triggering attacks, dust mites also may play a role in a person becoming sensitive, or allergic, in the first place.

"People who are exposed to high levels [of dust mite allergens] have greater odds of developing asthma than people who aren't exposed to these allergens," Zeldin says. "This suggests that exposure to mite allergen at high concentration levels is a strong independent risk factor for development of asthma."

Saying this is a cause-and-effect, however, "is a jump I'm not prepared to make at this point. It certainly contributes," he says.

"If you take folks sensitive to mite allergens who have asthma and remove them from mite-infested environments, their asthma gets better," Zeldin says.

Zeldin says researchers believe it would take a level as low as 2 micrograms of mites per gram of dust to keep a person from developing sensitivity to the allergens.

"Our study was able to drop the levels below 10 in the bedrooms, and that's good, but we were unable to get the levels down to 2," he says.

Diligent washing and vacuuming, as well as sealing mattresses from mites still might not be enough to stem the development of allergic sensitivity, he says.

Research underway in homes in Raleigh, N.C., and in Boston is exploring additional methods, he says.

What To Do

Using hardwood floors instead of carpeting and furniture upholstered with leather might make a home less inviting to mites, but not everyone can afford those expensive options, Zeldin says. "The best methods that we recommend are the ones focused in the bedroom, the ones that will most likely impact the disease," he says.

Ellis says controlling the temperature and humidity in your home helps, too. Dust mites thrive at temperatures from 68°F to 77°F and humidity levels of 70 percent to 80 percent, she says.

Washing sheets and blankets weekly in water that's at least 130°F should help control them, she says.

So should removing anything that mites find attractive, like tons of books in a room or any type of clutter. "And they love stuffed animals," Ellis says.

For additional tips to reduce the dust mite population in your home, visit the National Institute of Environmental Health Sciences.

Or, for more information on dust mite allergies, go to or the Asthma and Allergy Foundation of America.

INTERVIEWS with Darryl Zeldin, M.D., head of clinical studies section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, N.C.; Maryanne Ellis, executive director, Maryland-Greater Washington, D.C., chapter, Asthma and Allergy Foundation of America, Baltimore; August 2001 Environmental Health Perspectives
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