House dust mite

Family Pyroglyphidae belonging to the subclass Acari(mites). The subfamilies Dermatophagoidinae (D. pteronyssinus, D. farinae) and Pteroglyphidae (Euroglyphus maynei) belong to this family. Size: 170-500 μm, grey-white in colour; almost transparent; chitinous carapace with fine striated pattern; little hair. House dust mites have cutting and chewing mouth parts and live as commensals in the house dust of human dwellings. D. pteronyssinus (skin-eating feather mite) is the main source of the house dust allergen. E. maynei has a lesser significance. In the USA the Dermatophagoides farinae mite is more common. Main allergens are: Dermatophagoides pteronyssinus I and II (The p I and II). S.a.u. mites.

Both house dust mites and storage mites communicate through pheromones. They transmit 3 basic messages: alarm, aggregation, sexual behaviour. Neral (see Citral below) plays an important role as a volatile pheromone.

The Dermatophagoidines species feed on human skin scales as well as on microorganisms and certain moulds which are responsible for the breakdown of the lipid-containing components of the scales. Other organic material such as food supplies or pollen is also consumed.

The natural biotope of house dust mites is primarily the bed (mattress, duvet and pillow). Here sufficient materials are found as a source of food. Humans lose about 1 g of dandruff per day; this amount is sufficient as a food source for 1 million mites.

The microclimate is important. Optimal temperatures for mites are < 30 °C with a humidity of 70-80%. The minimum humidity must be at least 55%. Reproduction only at humidity > 60%. In heated dwellings there is relatively low air humidity, unfavourable living conditions for mites. Regular ventilation of the rooms also lowers the humidity! Local climatic factors such as the location of a house (e.g. southern slope, southern latitude and high mountain climate with relatively low humidity values prevent mite growth.

The mite population in carpets and rugs fluctuates with the seasons, increasingly in the summer months, when the room humidity is at its highest when central heating is switched off (Klimek L 2018). At the beginning of the summer, following the heating period, the mite population is small, and reaches a maximum in late summer. In late autumn and winter the mite population drops to a minimum again.

D. pteronyssinus, D. farinae and Euroglyphus maynei are present in all parts of the world. Transfer from one home to another can be made via articles of daily use and the human being himself. Occurs most frequently (humidity) in autumn months. Damp houses harbour 10 times more mites than dry ones. Several dozen mite species are found in house dust; D. pteronyssinus is involved to 70%. The number of mites can be as high as 10,000 per gram of house dust. House dust mites produce up to 4 eggs a day, during their entire life span this amounts to 80-300 eggs.

The concentration of house dust mites in bedrooms is 100 times higher than in the living room.

House dust mites also colonize hen houses in larger quantities. Under certain circumstances, this fact can be of relevance for occupational allergies. S.a. mite allergens.

1. Boulay ME et al (2003) The relationships between atopy, rhinitis and asthma: pathophysiological considerations. Curr Opin Allergy Clin Immunol 3: 51-55
2. Bronswijk van JEMF (1978) House dust mites, occurrence and significance. Allergology 1: 55-60
3. Franz JT et al (2009) House dust mites as a source of allergens in chicken houses. Allergo J 19: 106-109
4. Klimek L (2018) House dust and storage mites. Skin 01: 11-14
5. Kütting B et al (2001) The mite crustacean mollusc syndrome. dermatologist 52: 708-711
6. Loan R et al (2003) House dust-mite allergen and cat allergen variability within carpeted living room floors in domestic dwellings. Indoor Air 13: 232-236
7. Mortemousque B et al (2003) House-dust mite sublingual-swallow immunotherapy in perennial conjunctivitis: a double-blind, placebo-controlled study. Clin Exp Allergy 33: 464-469
8. Sidenius KE et al (2002) House dust mites and their allergens at selected locations in the homes of house dust mite-allergic patients. Clin Exp Allergy 32: 1299-1304
9. Terreehorst I et al (2003) Evaluation of impermeable covers for bedding in patients with allergic rhinitis. N Engl J Med 349: 237-246
10. Woodcock A (2003) Control of exposure to mite allergen and allergen-impermeable bed covers for adults with asthma. N Engl J Med 349: 225-236