Relatives of the spider, dust mites are microscopic arachnids that live indoors in household dust. Dust mite feces contain a protein that is a powerful allergenfor many people.

Over time, the waste dries up and turns to powder, allowing it to become airborne. When an allergic person inhales the powder, an allergic reactionor asthma attackoften follows.

There are several steps allergic individuals can take to reduce their household exposure to dust mites. These include thoroughly dusting and vacuuming the home at least once a week and using air conditioning and dehumidifiers to help reduce humidity. Research conducted by scientists at the Municipal Institute of Medical Research in Barcelona, Spain, suggests that replacing mattresses and adding more ventilation can also help control levels of the allergen.

During the study, the researchers analyzed dust samples to establish the distribution of two common house dust mites (Der 1 and Der 2). Dust samples were collected during home visits with 3,580 participants of the European Community Respiratory Health Survey II from 22 study centers in 10 European countries. The linens were removed from one bed in each home and a rectangular template was placed on the section of the bed where the participant typically slept. The area was then vacuumed to collect the dust samples. The researchers also used observations and interviews to collect information on housing characteristics.

After reviewing their data, the researchers found that Der 1 allergens were detectable in 68 percent of the samples, while Der 2 was detectable in 53 percent of the samples. In addition, large differences in allergen levels were discovered between study centers.

A number of major risk factors for high dust mite allergen levels were also discovered, including older mattresses, limited ventilation in the bedroom and the level of dampness in the bedroom.

These findings suggest that people can reduce their level of exposure to dust mite allergens by regularly replacing their mattresses and increasing ventilation in the bedroom, particularly during the winter.

Details of the study were released by the American Academy of Allergy, Asthma & Immunology in a press release. The full study appears in the articles in press area of the Journal of Allergy and Clinical Immunology (JACI) Web site.

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