Invertebrates
Dust Mite
Dermatophagoides · also called dust mite, house dust mite
A dust mite is an animal you will never see, sharing your bed by the million, living on the skin you shed while you sleep. It does not bite, burrow, or spread disease. What it does is fill your mattress with allergen — in its droppings and cast skins — and for a large share of people with asthma or year-round hay fever, that is a daily problem.
Overview
House dust mites are tiny arachnids (relatives of ticks and spiders) in the genus Dermatophagoides, about 0.25–0.3 mm long and translucent — right at the edge of visibility. They live in mattresses, bedding, carpets, and upholstery worldwide, and eat the flakes of dead skin people and pets constantly shed, plus the mould that grows on it.
Why they matter
The dust mite itself is harmless to the touch — no bite, no sting, no disease. The problem is its waste: about 20 droppings a day, wrapped in protein-rich membranes, plus shed skins and dead bodies. Proteins in these are among the most important indoor triggers of allergic rhinitis and asthma worldwide, and the allergen builds up in a mattress for years.
Living on humidity
Dust mites cannot drink — they absorb water vapour straight from the air — so they thrive in warm, humid homes and die back below about 50% relative humidity. That is why humidity control is the single most effective way to reduce them, alongside allergen-proof covers and hot-washing bedding.
Status
Not evaluated and in no way at risk — one of the most successful animals of the human-built environment, descended from mites that lived in bird and mammal nests, a niche a house closely resembles.
Dust Mite: common questions
Do dust mites bite?
No. The house dust mite does not bite, sting, burrow, or come onto the body at all. It lives in dust, bedding, and furnishings and feeds on shed skin flakes and mould, and it has no interest in and no way of feeding on a living person. Itchy bumps that people blame on dust mites are usually caused by something else, such as bed bugs, fleas, bird or rodent mites, scabies, or skin reactions. What the dust mite does cause is allergy, through the proteins in its droppings and shed skins, which is a different mechanism from biting.
How do dust mites cause allergies and asthma?
Not by contact but by what they leave behind. A dust mite produces about twenty droppings a day, and these, along with its cast skins and dead body fragments, contain proteins that the immune systems of sensitised people treat as a threat. Breathing in the fine dust that carries these particles triggers the release of histamine and other chemicals, producing a blocked or runny nose, sneezing, itchy eyes, and, in people with asthma, airway inflammation and wheezing. Because the allergen sits in mattresses, carpets, and soft furnishings, exposure is constant and year-round rather than seasonal.
How do I reduce dust mites in my home?
The most effective single measure is controlling humidity, keeping indoor relative humidity below about 50 percent with ventilation and heating or a dehumidifier, since the mites cannot survive dry air. For an allergic person's bedroom, the standard steps are encasing the mattress, duvet, and pillows in tightly woven allergen-proof covers, washing bedding weekly at 55 degrees Celsius or hotter, removing carpets, heavy curtains, and clutter that trap dust, and vacuuming with a machine fitted with a good filter. These reduce exposure substantially, though they do not make a home mite-free.
Are dust mites the same as bed bugs?
No, they are completely different. Dust mites are microscopic, invisible without magnification, do not bite, and cause problems only through allergy. Bed bugs are visible insects, up to about five millimetres, roughly the size of an apple seed, that come out at night to bite people and drink blood, leaving itchy welts, and that hide in the seams of mattresses and in furniture and skirting. If you are getting rows of itchy bites overnight, that points to bed bugs or fleas, not dust mites.