Human scabies is caused by Sarcoptes scabiei var. hominis, a mite within the epidermal layers. Transmission occurs after skin contact with an infected individual or possibly from infested clothing and bedding. The female mite burrows into the skin and deposits two to three eggs daily. Fecal pellets (scybala) are deposited in the burrow and may be responsible for localized pruritus, often nocturnal. The pink white, slightly elevated burrows are typically seen in the web spaces of the hands and feet, penis, buttocks, scrotum, or extensor surfaces of the elbows and knees. Crusted, or Norwegian, scabies seen in immunosuppressed or debilitated patients (see HIV chapter) usually present with asymptomatic acral crusting, but can occur anywhere.
Management and Disposition
Topical 5% permethrin cream is commonly used. Apply from the neck to the toes overnight (8-12 hours) and then wash off. Repeat in 7 days. Bedding, towels, and clothing should be washed in hot water and dried on high heat (an alternative is to place items into a plastic bag for 10 days).
Scabies. Note the scaling, erythema, and thickening of the skin at the finger bases. This describes chronic infection and potential to develop crusted scabies. (Photo contributor: David Effron, MD.)
Scabies. Burrows and erosions in an infant. (Photo contributor: Lawrence B. Stack, MD.)
Scabies. Extensive burrows and erosions. (Photo contributor: David Effron, MD.)
Intimate contacts and all family members in the same household should be treated.
Patients often experience “postscabietic itch,” which can last for 2 to 4 weeks. This is not a new infestation but rather an immunologic reaction to the dead mite. Confirm completion of an appropriate treatment.