House dust mite

The dust mites are cosmopolitan members of the mite family Pyroglyphidae.

A scanning electron micrograph of a female dust mite

House dust mites, due to their very small size and translucent bodies, are barely visible to the unaided eye.[2] A typical house dust mite measures 0.2–0.3 mm (0.008–0.012 in) in length.[3] For accurate identification, one needs at least 10× magnification. The body of the house dust mite has a striated cuticle.

They feed on skin flakes from animals, including humans, and on some mold. Dermatophagoides farinae fungal food choices in 16 tested species commonly found in homes was observed in vitro to be Alternaria alternata, Cladosporium sphaerospermum, and Wallemia sebi, and they disliked Penicillium chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum.[4]

The predators of dust mites are other allergenic mites (Cheyletiella), silverfish and pseudoscorpions.[5]

The average life cycle for a house dust mite is 65–100 days.[6] A mated female house dust mite can live up to 70 days, laying 60 to 100 eggs in the last five weeks of her life. In a 10-week life span, a house dust mite will produce approximately 2,000 fecal particles and an even larger number of partially digested enzyme-covered dust particles.

Dust mites are found worldwide, but are found more commonly in humid regions.[7] The species Blomia tropicalis is typically found only in tropical or subtropical regions.[8] Detectable dust mite allergen was found in the beds of about 84% of surveyed United States homes.[9] In Europe, detectable Der p 1 or Der f 1 allergen was found in 68% of surveyed homes.[10]

The mite's gut contains potent digestive enzymes (notably Peptidase 1) that persist in their feces and are major inducers of allergic reactions such as wheezing. The mite's exoskeleton can also contribute to allergic reactions. Unlike scabies mites or skin follicle mites, house dust mites do not burrow under the skin and are not parasitic.[11]

Severe dust mite infestation in the home has been linked to atopic dermatitis and epidermal barrier damage has been documented.[12]

House dust mites are associated with allergic rhinitis and asthma,[13] as well as allergic conjunctivitis.[14] Efforts to remove these mites from the environment have not been found to be effective.[13] Immunotherapy may be useful in those affected.[13] Subcutaneous injections have better evidence than under the tongue dosing.[15] Topical steroids as nasal spray or inhalation may be used.[16]

Dermatophagoides spp. can cause oral mite anaphylaxis (AKA pancake syndrome) when found in flour.[17][18]

Furniture with wooden or leather surfaces reduce the dust mite population.[21]

Dust mite-proof encasements to mattress, pillow, and duvet, prevents chronic contact with allergens.[16][21]

Hot tumble drying a bed linen for 1 hour will kill 99% of mites therein.[22]

Weekly changing the bed linen reduces the risk of exposure to dust mites.[16]

Cotton covers not covered with complete mattress covers are very likely to become colonised by bacteria and molds; they must be cleaned periodically (at least every second to third month). Here, the dust mites are beneficial as they return cotton to its original state after it has degraded by contact with bare skin. [23]

Dust mite eggs are freeze tolerant (−70 °C for 30 minutes); hatching can normally be prevented by exposure of fabrics to:[24]

• Direct sunlight for 3 hours or
• Dry or wet heat of at least 60 °C (140 °F) for a minimum of 30 minutes.

Dust mites drown in water.[25]

Good properties of anti-mite fabrics have been identified as being:[26]

• Thread count greater than 246.
• Pore size of between 2 and 10 microns.
• Allergen impenetrability >99%.
• Dust leakage of less than 4%.
• Breathability between 2 and 6 cm³/second/cm².

Allergy patients are advised to keep the relative humidity below 50%, if possible. Very few mites can survive if the humidity is less than 45% (at 22 °C (72 °F)). However, they can survive if the humidity is high just for an hour and a half per day, for example due to cooking.[25]