House dust mite
The house dust mite
), sometimes abbreviated by allergists to HDM, is a cosmopolitan guest in human habitation. It is more common in Europe than North America, where it is replaced by D. farinae
. The mite thrives in modern fully-carpeted, double-glazed, draught-proof homes, and is comfortable at 25C, 75% relative humidity.
The mite lives on shed human skin cells, predigested by a fungus Aspergillus repens. It is particularly common in carpets and bedding.
The house dust mite is one of the most important allergens, implicated in allergic asthma, rhinitis, conjunctivitis and dermatitis. The protein responsible for the allergic reaction is DerP1, a protease digestive enzyme found in mite feces.
Measures to control house dust mite include:
- Regular vacuum cleaning (especially with high-efficiency particulate air (HEPA) filters)
- Regular damp dusting of surfaces
- Replacement of carpets with vinyl flooring
- Covering of mattresses and pillows with impervious materials
- Daytime internment of teddy bears in a freezer
- Use of chemicals (acaricides) to kill mites
- Use of fungicides to kill Aspergillus
These measures, while reducing numbers of HDM and amounts of allergen, seem to have only marginal effects on allergic symptoms.