Related to ticks, mites are an extremely successful group of insect-like invertebrates. Their success is due in part to their microscopic size and also to their ability to thrive in a wide variety of habitats. Most mites prey on animals, including mammals, birds, and other insects. Mites rarely transmit disease directly but, because they often cause intense itching, their bites can serve as entry points for infection. In addition to the effects of their bites, mites can cause allergies that affect breathing, like asthma, or the skin, like eczema. Different types of mites have different effects in humans--effects that often resemble other conditions, like contact dermatitis or simple mosquito bites.
In their later stages of life, harvest mites only affect insects. However, in their larval stage they bite humans or other mammals. Harvest mite larvae are called “chiggers.” Probably the mite that most commonly affects humans, a chigger's bite is painless as it is happening. It is not until later that the effects can been noticed. After the microscopic creature finishes feeding, it falls from the host and leaves in its wake a red swelling with a hard, white center. This welt comes with intense itching that is not terribly painful to scratch. Beware, though, because this may lead to too much scratching and a broken bite may allow further infection to invade. Welts generally have delayed onset, meaning they don’t form immediately upon exposure, and they may be accompanied by a mild fever.
Scabies mites fit into several groups, each of which prefers a specific species for feeding. Some choose humans to serve as hosts. They live their entire lives (about two weeks) in their host, who may not notice them for up to a month, depending on previous exposure. Scabies mites actually burrow into the skin, where they lay eggs. The discomfort scabies causes tends to be particularly intense at night, so patients sometimes suffer from lack of sleep. Redness and itching are the first signs but this may develop into a rash that includes small welts at the base of hairs. These may develop on most of the body, including the thighs, calves, armpits, and wrists.
Dust mites don’t actually bite humans but they do have distressing effects. They generally feed on flakes of dead skin so they live in places like upholstered furniture and mattresses. They and their feces may become airborne, triggering allergic reactions in humans. These reactions include respiratory effects, like asthma attacks, and dermatological symptoms, most often a red, itchy rash. Dust mites do best in humid environments, so consistently low humidity in the home can keep dust mites at bay.
Itch mites generally prefer insects to humans, but people who are in frequent contact with hay, grass, and seeds may be bitten. The bite itself isn’t felt but will cause the later (about 12 hours) onset of a small red swelling with a pimple-like elevation at the center. Itch mite bites are particularly painful when scratched. They usually bite unprotected areas like the face and arms. For the most part, humans are relatively safe from itch mites but, with an itch mite population boom, the mites will take any host they can get. They cannot, however, live on humans nor can they survive indoors, so they are not a huge threat.
Rodent and Bird Mites
As their name suggests, rodent and bird mites prefer rodents (mice or rats, depending on the specific type) and birds (including chickens and pigeons) to people. However, if these mites find themselves without a host, they are willing to bite humans. Rodent and bird mites are blood-suckers, and leave inflammation and redness around the bite. As with other mite reactions, intense itching usually accompanies exposure.