Scabies is caused by a mite, Sarcoptes scabiei hominis, which burrows superficially into the skin and is transmitted by person-to-person contact. The finger webs of the hands, wrists, axillae, nipples, buttocks and genitalia (and the face in children) are most vulnerable. Involvement of the head and neck can occur in infants and in immunocompromised individuals. Intense itching, particularly at night, heralds the development of localized, erythematous, excoriated lesions which appear about 6-8 weeks after the initial infestation. Papular and urticarial lesions may later occur anywhere on the body. A presumptive diagnosis can be made on the basis of clinical findings and a history of itching, particularly at night. Massive infestation, often associated with extensive crusting of the skin, sometimes occurs in elderly or immunocompromised patients.

Prevention and management

All persons in the household must be treated to prevent infestation or reinfestation. Benzyl benzoate is an inexpensive scabicide. It should be applied to all skin surfaces, from the scalp to the soles of the feet, and care should be taken to avoid contact with the eyes. It is not necessary to bathe before application; however, clothing and bedding should be washed or left outside exposed to the air for 72 hours to prevent reinfestation. A 25% lotion applied once daily at night on 2 consecutive days is commonly used. This is often followed by a single application at night 3 days later. Permethrin, 5% cream, is equally effective and less of an irritant, but more expensive. A cheaper alternative is lindane, but it should not be used in infants or young children since it may cause seizures. It also accumulates in the environment. A more suitable alternative for young infants is 6-10% precipitated sulfur in a cream or paste, which is applied once daily for 7 consecutive days.

Other scabicides and pediculicides which are formulated as lotions or shampoos include sulfiram, carbaril, crotamiton and phenothrin.