Scabies is an itchy skin condition that is caused in humans by a mite called Sarcoptes scabiei. Humans, dogs and cats are affected by their own distinct species of mite. People may show a temporary skin reaction from contact with the animal scabies mite, but it is unlikely to develop full-blown scabies from this source. Scabies is a contagious skin disorder that can spread rapidly through close physical contact in a family, child care group, school class, nursing home, or prison. Less often, sharing clothing or bedding with an infected person can spread the mites.
The female mite burrows just beneath the skin and produces a tunnel in which it deposits eggs. After the eggs hatch, the mite larvae head to skin surface, where they mature and can spread to other areas or to the skin of other people. The microscopic examination can determine the presence of mites or their eggs.
Scabies signs and symptoms include itching and thin, irregular burrow tracks made up of tiny blisters or bumps on the skin. Clinical manifestations are observed in patients, affected for the first time, after a period of six weeks. In people previously suffered from the disease, symptoms and signs may develop within a few days of exposure. Particularly, the presence of mites results in intense itching in the affected skin area. The itching is related to the body's allergic reaction to the mites, their eggs and their waste. The urge to scratch may be especially strong at night. Vigorous scratching can break the skin and allow a secondary bacterial skin infection to occur. Bacteria (staphylococci, streptococci) can cause a superficial skin infection (impetigo). The burrows or tracks typically appear in folds of the skin. In adults and older children, scabies is most often observed between fingers, in armpits, around the waist, along the insides of wrists, on the inner elbows, on the soles of the feet, around breasts, around the male genital area, on buttocks, on knees, and on shoulder blades. In infants and young children, common sites of infestation include the scalp, face, neck, palms of the hands, and soles of the feet.
Norwegian scabies (crusted scabies) is a more severe form of the disease that may affect certain high-risk groups, such as people with chronic health conditions that impair the immune system (e.g. AIDS, chronic leukemia), patients in hospitals or nursing facilities, and older people in nursing homes. Norwegian scabies tends to cover large body areas and to be crusty and scaly. It is very contagious and can be hard to treat.
The treatment includes medications that are applied to the skin in order to kill the mites and their eggs. Several creams and lotions are available with a doctor's prescription. Moreover, antihistamines relieve the allergic symptoms associated with the presence of mites. Treatment is often recommended for all household members and other close contacts, even if they show no signs of scabies infestation.