This summary discusses adult patients. Scabies in children is addressed separately.

Scabies is an intensely pruritic eruption caused by the mite Sarcoptes scabiei var. hominis. It is transmitted most often via direct person-to-person contact and less frequently by fomites. It is extremely contagious, spreading between individuals who share close contact or living spaces.

Nocturnal itching is a classic symptom. In a typical infestation, there are 10-20 mites. Most patients mount an intense hypersensitivity reaction to the mites, which burrow into and just below the stratum corneum of the epidermis. This results in a widespread and highly pruritic eruption. The hypersensitivity reaction usually develops 2-6 weeks after initial infestation.

Nodular scabies refers to the presence of pink to red nodules that represent a localized intense hypersensitivity reaction to retained mite parts or antigen. The presence of mites within these nodules has also been reported, but nodular scabies may be seen even after the infestation has been successfully treated. Typical sites include the lower abdomen and buttocks.

Persons with human immunodeficiency virus (HIV) infection and others who are immunosuppressed are at increased risk for crusted scabies.