Definition
House dust mites are microscopic creatures of the Pyroglyphidae family in the class Arachnida. The most important species for allergy are Dermatophagoides pteronyssinus and D. farinae. Storage mites (Acaridae, Glycyphagidae) are particularly relevant where grain and food are stored.
Biology
House dust mites measure 0.2–0.3 mm and cannot be seen with the naked eye. They thrive best at 20–25 °C and 70–80% relative humidity; below 50% humidity they struggle to survive. Under suitable conditions, development from egg to adult takes about a month.
Most of the allergen is found in mite faecal particles. These particles, 10–40 µm in diameter, accumulate in mattresses, carpets and upholstery; activities such as making the bed or dusting briefly make them airborne, after which they settle again within about 20–30 minutes.
Mite allergens
Around 40 allergen groups have been identified from mites so far. Of these, Der p 1 and Der p 2 are the major allergens causing sensitisation in most patients; in recent years Der p 23 has also been recognised as a major allergen. Identifying allergens at the molecular (component) level guides physicians, particularly when planning allergen immunotherapy.
There is marked cross-reactivity among Dermatophagoides species, whereas cross-reactivity with storage mites is more limited.
Mite allergy is diagnosed by skin prick testing or by measuring specific IgE in the blood. If you have symptoms, see an allergy specialist.
This article is for general information only; consult your physician for diagnosis and treatment.
