The human itch mite infects people of all ages, social classes and races the world over. The American Osteopathic College of Dermatology estimates that more than 300 million people become infested with the human itch mite each year. The infestation, called scabies, frequently occurs in crowded environments such as those found in day care centers, jails and nursing homes. Scabies transmission occurs through prolonged skin-to-skin contact. According the Centers for Disease Control and Prevention, adults commonly acquire scabies through sexual contact with an infected partner. The mite variety that infects humans feeds exclusively on human skin. Dogs, cats and other animals do not transmit scabies to people.
The mites are microscopic, wingless, parasites that bite skin and feed off tiny amounts of human blood. Their bite causes an inflammatory skin response and often itching and burning of the skin. Typically, the itching sensation intensifies at night.
The female mite is attracted by warmth. Crevices and folds in human skin offer the warmth she craves, as well as protection. Common infestation sites include the creases between the fingers and toes, the underarms, groin area, between the thighs, between the buttocks, around the nipples, and within fat folds. The mite also hides at the waistline, under watch bands and bracelets, and even under fingernails.
Rashes are also common in mite infestations as the body develops an allergic response to the mite's secretions. Mite-infested skin becomes red and inflamed and small pimple-like infections, can develop. The scabies rash resembles hives.
When diagnosing a mite infection, doctors frequently look for trails just below the surface of the skin, within the epidermis. These trails indicate where the female mite has tunneled to lay her eggs. The burrows appear as raised, bumpy grayish-white or skin colored lines.
A particularly severe form of scabies, called Norwegian scabies, or crusted scabies, frequently occurs in people with compromised immune systems, in the infirm and in the elderly. Crusted scabies is an indication of the number of mites rather than a variation of mite. Some people with this infestation have more than two million mites feasting on their skin at a time. In response to the overwhelming number of bites it receives, the skin thickens and crusts.
Because of the sheer number of mites involved in a Norwegian scabies infestation, the risk of contagion increases exponentially. Transmission not only occurs through direct skin-to-skin contact, but can also occur through contact with the clothing and/or bedding of an infested individual.