Scabies is a skin infestation by a tiny mite that burrows into the top layer of skin and triggers an intensely itchy allergic reaction. It spreads by prolonged skin contact, so households, nursing homes and shelters are common settings.
Key symptoms
- Intense itching, worse at night
- Small itchy bumps on the hands, wrists, waist and genitals
- Other people in the home with the same itch
- In infants, rash on the palms, soles and scalp
What you find on exam
- Thin, wavy, gray burrows, mostly in the finger webs and wrists
- Small red papules, scratch marks and sometimes blisters
- Nodules on the genitals, armpits or buttocks
- Thick, crusted, scaly plaques in crusted scabies
- Signs of secondary bacterial infection: crusts, pus, cellulitis
Tests
- Often a clinical diagnosis based on itch, burrows and contacts
- Skin scraping with mineral oil under the microscope: mites, eggs or feces
- Dermoscopy may show the mite at the end of a burrow
Treatment basics
- Permethrin 5 percent cream from neck to toes, left overnight and repeated in 1 to 2 weeks
- Oral ivermectin as an alternative, with a second dose 1 to 2 weeks later
- Treat all close contacts at the same time, even without symptoms
- Wash bedding and clothes in hot water or seal them in a bag for 3 days
- Itch can last 2 to 4 weeks after cure; use antihistamines and moisturizers
Red flags
- Thick crusted plaques in an older or immunocompromised patient (crusted scabies)
- Fever, spreading redness or pus from infected lesions
- Outbreak in a nursing home, hospital ward or shelter
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.