There are multiple kinds of biting mites. Chiggers are probably the most common. Chiggers are mite larvae that are ubiquitous outdoors except in arid regions; they bite, feed in the skin, then fall off. Outside the US, chiggers may carry Rickettsia tsutsugamushi (see Rickettsiae and Related Organisms: Scrub Typhus). They do not burrow into the skin, but because they are small, they are not readily seen on the skin surface.
Common mite species that bite and burrow into the skin include Sarcoptes scabiei, which causes scabies (see Parasitic Skin Infections: Scabies), and Demodex mites, which cause a scabies-like dermatitis (sometimes referred to as mange).
Dermatitis is caused by mites that occasionally bite humans but are ordinarily ectoparasites of birds, rodents, or pets and by mites associated with plant materials or stored food or feed.
Allergic dermatitis or grocer's itch is caused by several species of mites associated with stored grain products, cheese, and other foods. These mites do not bite but cause allergic dermatitis because people become sensitized to allergens on the mites or their waste products.
House dust mites do not bite but feed on sloughed skin cells in pillows and mattresses and on floors (especially on carpets). They are significant because many people develop pulmonary hypersensitivity to allergens in the exoskeletons and feces of house dust mites.
Symptoms and Signs
Most bites cause some version of pruritic dermatitis; pruritus due to chigger bites is especially intense.
Diagnosis of nonburrowing mite bites is presumptive based on the patient's history (eg, living, working, and recreational environments) and physical examination. The mites themselves are rarely found because they fall off after biting, the skin reaction is usually delayed, and most patients seek a physician's assistance only after several days. Lesions caused by different mites are usually indistinguishable and may superficially resemble other skin conditions (eg, other insect bites, contact dermatitis, folliculitis).
Diagnosis of burrowing mites can often be made presumptively based on history and a scabies-like pattern of skin lesions. If the diagnosis is unclear or if treatment is ineffective, the diagnosis can be confirmed by skin biopsy.
Treatment of nonburrowing mite bites is symptomatic. Topical corticosteroids or oral antihistamines are used as needed to control pruritus until the hypersensitivity reaction resolves. Through discussion of possible sources, the physician can help patients avoid repeated exposure to mites. For Demodex bites, veterinary consultation is needed.
Last full review/revision February 2013 by Robert A. Barish, MD, MBA; Thomas Arnold, MD