House dust mitesDermatophagoides spp. — habitat, diet and reproduction

• A dust mite is much smaller than one millimetre.
• Adults have eight legs rather than the six of insects.
• Their main food includes shed skin, not blood.
• Allergens can remain in dust after a mite dies.

The small oval body is pale, with fine surface markings visible under magnification. Dust mites have no wings.

At around 0.3 mm long, their details are difficult to see unaided. Microscope photographs greatly enlarge the animals and do not show life size. Mites are arachnids, as are spiders, but not every mite is a house dust mite: other groups have different diets, hosts and relationships with people.

Dust mites move among fibres and particles that provide many small shelters. They neither jump nor fly. Moisture is important, and warm humid places with food can support more mites than dry exposed surfaces.

They cannot be identified from a supposed bite mark because they do not bite. Itching or sneezing alone also cannot establish their involvement; many factors cause similar symptoms.

Mattresses, bedding, upholstery and some carpets provide food and refuge. Frequently used areas accumulate organic particles, including shed skin cells.

Indoor conditions matter beyond the mere presence of dust. Humidity, temperature and furnishings affect the habitat. These organisms occur in homes across many regions, but an ordinary photograph of dust cannot automatically identify a speck as a mite.

The main food includes flakes of skin shed by people and animals. Other microscopic materials, including pollen and fungal spores, may also be consumed.

Unlike blood-feeding or skin-burrowing parasites, house dust mites use organic material in their surroundings. This contributes to the breakdown of fine debris. Their health significance comes from allergenic proteins rather than attacks on skin during feeding.

Females lay eggs that produce juvenile stages. Development involves changes and moults before adulthood. Under favourable conditions, reaching adulthood can take approximately one month. Lifespan is measured in months but varies with species and surroundings.

A population may contain eggs, juveniles and adults together. Living mite numbers are not the same as allergen levels: body fragments and waste can persist after the animals die.

The common name refers to their household habitat. Dermatophagoides is a genus, and Dermatophagoides pteronyssinus is the species pictured here.

Research into household dust helped establish links with some allergies. Scientists can measure allergenic proteins in samples without seeing each animal separately. Although all mites are arthropods, differences between their groups matter when discussing food and effects on people.

For household dust mites, the main concern is their relationship with indoor environments and allergic individuals. Proteins in bodies, secretions and waste can trigger symptoms in susceptible people.

Reducing dampness and regularly caring for textiles can limit suitable habitat and allergen accumulation. Completely removing every mite from a home is unrealistic. Persistent symptoms warrant medical assessment to identify their cause; these animals are not biting or stinging insects.

Do house dust mites bite?

No. They can produce allergens but do not bite or feed on blood.

Can they be seen without magnification?

They are very small, usually below 0.5 mm, and details require magnification.

What do they eat?

Mainly already-shed skin flakes and other microscopic material.

Do allergens disappear when a mite dies?

Not immediately. Allergenic proteins can remain in body fragments and waste in dust.