December 10th, 2018
Dust mites are 8-legged arthropods that live in the house dust of homes located in regions where they are prevalent. They have been recognized as the major source of allergens in house dust since 1967. The most common species found in homes in temperate regions of the United States are Dermatophagoides farinae and Dermatophagoides pteronyssinus. In addition, others, such as Blomia tropicalis, can be found in homes in tropical and subtropical regions.
Dust mites feed on organic materials, including skin scales, fungi, yeasts, and bacteria. Because they are composed of approximately 75% water by weight, they maintain their water balance through uptake of water vapor when RH is at least approximately 65%. They are susceptible to water loss when humidity decreases below 65%and have decreased survival and reproduction with an RH below 50%.
Mites produce and excrete numerous allergens into the envi-ronment, including cysteine proteases such as Der p 1 and Der f 1, serine proteases including Der p 3, 6 and 9, and proteases that can activate protease-activated receptor-2, which are proinflammatory in humans through a noneIgE-dependent mechanism. Mites also produce glycosidases and carbohydrate-binding proteins and muscle, cytoskeleton, and calcium-binding proteins. There is cross-reactivity among various mite species and between mites and other related families, such as crustaceans and cockroaches.
Tests for measurement of mite allergens from environmental samples are commercially available. Such tests have included measurement of guanine as a proxy for fecal material and of specific allergens using polyclonal and monoclonal antibodies. The most commonly used assays are for the measurement of Der p 1 and Der f 1. Assays for Der p 2, Der f 2, and Blo t 5 also are available. Recently, a new set of international standards for dust mite allergens that have been standardized using molecular techniques has led to a revision of the concentrations reported in earlier studies of mite exposure. This may require a reassessment of exposure thresholds associated with the development of sensitization, disease, and morbidity.