Dust mite allergy

What it is

Dust mites are tiny creatures with eight legs. They are not true insects but relatives of spiders, and they are too small to see without a microscope or magnifying glass.¹ They feed on organic material, including flakes of skin, fungi, yeasts and bacteria.² In temperate parts of the US, the two most common species in homes are Dermatophagoides farinae and Dermatophagoides pteronyssinus. In tropical and subtropical areas, other mites such as Blomia tropicalis can also be found in homes.²

The allergen comes mostly from what mites leave behind. In mite cultures, more than 95% of the allergen that builds up is tied to their fecal particles.² Their body parts can also trigger asthma in people who are allergic to them.⁵ The AAAAI calls the dust mite the number one indoor allergen.⁴

Symptoms it causes

Dust mite allergen causes a reaction when it is breathed in or comes into contact with the body.¹ Common symptoms include sneezing, a runny or stuffy nose, and red, itchy or watery eyes. Some people also have itching, coughing, wheezing, chest tightness and shortness of breath.¹ Symptoms can be present all year, and they often get worse during or right after vacuuming, sweeping or dusting.¹

Dust mites are closely tied to asthma, and they are a common cause of asthma in children.¹ The EPA notes that mite body parts and droppings can trigger asthma in people who are allergic, and that exposure can lead to asthma in children who did not have symptoms before.⁵ A practice parameter from US allergy societies describes sensitization to dust mites as a risk factor for developing asthma.²

Where it’s found

The EPA says dust mites are in every home. They live in mattresses, pillows, carpets, upholstered furniture, bedding, clothing, stuffed toys and other fabric items.⁵ They live deep inside soft materials, and their allergen is generally not found on hard surfaces.² An estimated 84% of US homes have detectable dust mite allergen.²

Mites need humid air to thrive. They prefer temperatures of 70°F or above with humidity of 75 to 80%, and they are not usually found in dry climates.¹ Their survival and breeding drop when relative humidity falls below 50%.² Mite allergen becomes airborne when dust is disturbed, and most of it settles again within about 15 minutes, so little is found in the air of an undisturbed room.²

US agencies and allergy societies describe these ways to cut exposure:

• Wash bedding in hot water every week and dry it completely.⁵
• Put dust-proof covers on pillows and mattresses.⁵
• Vacuum carpets and fabric furniture every week, ideally with a HEPA-filter vacuum, while the person with allergies is out of the room.⁵
• Keep indoor relative humidity between 35% and 50%.²
• Remove wall-to-wall carpet as much as possible; throw rugs can be used if they are washed or dry-cleaned regularly.³

Single steps may not be enough on their own. The practice parameter found that mite covers alone are unlikely to bring a clinical benefit unless they are part of a wider plan, and it recommends combining several measures.²