Aug. 6, 2001 -- When it comes to battling allergy-provoking substances in household dust, many people are unwittingly sleeping with the enemy: dust mites lurking in bedroom furnishings. But even simple, inexpensive steps such as washing bed linens weekly, cleaning or removing carpets, and using allergen-proof pillow and mattress covers can help keep allergies and asthma attacks at bay, experts say.
Although you can't see them, minute creatures called dust mites can be found just about anywhere humans live and sleep, including bedding, carpeting, draperies, and upholstery. The little devils feast on flakes of human skin sloughed off every day, and pay their human hosts back by giving off allergy-causing substances called allergens.
According to a recent study, nearly half of all homes in the U.S. are likely to have bedding that contains dust-mite allergens at levels high enough to provoke a possible allergic reaction. And, there are enough allergens present to trigger asthma in susceptible people in 22 million households.
A 1997 study by the National Institute of Allergy and Infectious Disease reported that the number of new asthma cases had risen sharply over the last several decades, and that the increase was particularly pronounced among children living in the inner-city.
Findings like this prompted Darryl C. Zeldin, MD, and colleagues from the National Institute for Environmental Health Sciences, or NIEHS, at the University of Washington, and Harvard School of Public Health to conduct a study to evaluate practical methods for lowering levels of dust-mite allergens in homes in low-income urban neighborhoods. The study is published in the August issue of Environmental Health Perspectives.
The researchers enrolled 39 households in the Seattle area. Participants were given mattress, box-spring, and pillow covers that are barriers against dust mites. All bedding was washed weekly by participants or in commercial laundries. Carpets were treated either with intensive vacuuming alone, or vacuuming followed by "dry" steam cleaning, which injects sterilizing steam rather than hot water into the fabric to kill allergens, which are then vacuumed back into the machine.
The researchers found that both bedding covers and laundering were effective at reducing allergens below asthma-triggering levels, as were vacuuming and dry steam cleaning of carpets and upholstery. Vacuuming alone also reduced allergen levels in carpets, but only for a short time.
"When you vacuum, there's a [temporary] reduction in the allergen, but it's pretty meaningless because the allergen can be deep within the carpet dust, and you only remove a very small portion of the dust [when you vacuum]," says indoor air-quality expert and author Jeffrey C. May, who runs a building inspection company in Cambridge, Mass. "The question is are you really removing enough of the allergen to relieve somebody of symptoms? I don't believe so."
May tells WebMD that dry steam cleaning, however, when combined with vacuuming, can be highly effective, because it destroys the allergens.
"We don't know whether these interventions work for other allergens; we're currently doing a study in Raleigh and in Boston looking at the dry steam cleaning method for cockroach-infested homes with high cockroach allergen levels," Zeldin, head of the clinical studies section at NIEHS, tells WebMD.