Curriculum · ENT, Ophthalmology, and Dermatology
Scabies
What it is
Scabies is a cutaneous infestation caused by the mite Sarcoptes scabiei. The mite burrows into the skin and lays its eggs in the stratum corneum. It typically affects children and young adults.
Causes and risk
It is spread by direct and prolonged skin to skin contact, and by fomites such as clothes and combs; in severe cases it is transferred from infested clothing, bedding or the environment. The incubation period is 3-4 weeks. The intense pruritus is due to a delayed type IV hypersensitivity reaction to the mites and eggs, which occurs about 30 days after the initial infection, so the itching is an allergic reaction to the mite, its burrow and its eggs.
How it presents
Pruritus is widespread and worse at night. There are linear burrows on the side of the fingers, in the interdigital webs and on the flexor aspects of the wrist, and multiple small erythematous papules, often excoriated. In infants the face and scalp may also be affected. Secondary features are seen from scratching: excoriation and infection. A friend in the same apartment may have the same rash.