Dust mites

Dust mites are tiny microscopic creatures that belong to the same family as spiders and ticks. They can be found virtually anywhere you find dust and are an important cause of allergic reactions to house dust. Dust mites are sustained by feeding off human and animals sloughs (skin cells). They live well and multiply easily in warm, humid places. They prefer temperatures at or above 70°F with a relative humidity of 75-80 percent and die when the humidity falls below 40-50 percent. Thus, heated indoor environments with low ventilation rates contribute to the proliferation of dust mites.

Allergy to dust mites comes from the human body's reaction to proteins found in the feces of the mites. This protein is generally found in high concentrations in pillows, mattresses, carpeting, and upholstered furniture. Allergens are released during housekeeping activities, but settle once the disturbance is complete. Thus, dust mites produce an indoor allergen that is an important risk factor for sensitization and respiratory allergy. It is estimated that approximately 10 percent of the general population and 90 percent of people with allergic asthma are sensitive to dust mites. Recent studies in the United States suggest that at least 45 percent of young people with asthma are allergic to dust mites ( American College of Allergy , Asthma, and Immunology).

Some risk exposure thresholds have been defined for dust mite allergens (i.e. concentration at and above which asthma can be triggered or sensitization may occur). It is estimated that there may be many as 19,000 dust mites in one gram of dust, but usually between 100 to 500 mites live in each gram ( American College of Allergy, Asthma, and Immunology) .

Dust mite allergens can be detected and quantified using an ELISA (enzyme-linked immunosorbent assay).