Dermatology

Scabies

A contagious infestation by Sarcoptes scabiei causing intense nocturnal itch, burrows and a papular rash; cure requires correct whole-body treatment and simultaneous treatment of relevant close contacts.

In a nutshell

Scabies is a contagious Sarcoptes scabiei infestation causing severe nocturnal itch, burrows and papules, commonly in finger webs, wrists, axillae, waist and genitalia. Diagnose clinically, treat the whole required skin surface twice one week apart, treat all relevant close contacts simultaneously and recognise crusted scabies as a high-transmission specialist problem.

Classic presentation

Severe nocturnal itch with finger-web burrows and an itchy household or sexual contact.

Key points

Burrows plus nocturnal itch and affected contacts are highly suggestive.
The face may be spared in adults but scalp and face can be involved in infants, older adults and crusted disease.
Use a licensed scabicide over the whole required skin surface and repeat treatment after 7 days.
Treat household and other close contacts at the same time, even if asymptomatic.
Post-scabetic itch can persist for weeks; new burrows or lesions are more concerning for failure or reinfestation.
Crusted scabies may itch little, is highly transmissible and needs specialist combination treatment and infection-control support.

First-line investigation

Clinical diagnosis with a full skin examination and contact history; use dermoscopy or scraping when uncertain or when crusted disease is suspected.

Management

Recognise crusted disease and infection

Escalate thick crusted scale, heavy shedding, frailty, immunosuppression, secondary infection, very young age or communal outbreak for specialist and infection-control support.^1,2,3

Treat the whole skin surface

Use a licensed scabicide selected for the person, applied thoroughly over the required whole skin surface and repeated one week later according to product and BNF instructions.^1,2,4

Treat contacts together

Coordinate treatment for household, sexual and other close skin-to-skin contacts, including asymptomatic contacts, rather than waiting for them to develop itch.^1,2

Limit transmission and relieve itch

Launder or bag clothing, towels and bedding on the first treatment day, avoid close contact until treatment has started and explain that post-scabetic itch may persist for weeks.^1,2

Use specialist treatment when needed

Seek specialist advice for crusted, paediatric, pregnancy-associated, resistant or outbreak disease; crusted scabies often needs combination topical and oral therapy.^1,3,4

Distinguish itch from treatment failure

Review new burrows, new lesions, application technique and contact treatment; investigate secondary infection or another diagnosis if symptoms persist or worsen beyond the expected post-treatment period.^1,2,3

Exam traps

Treat all relevant contacts at the same time, not just the person with itch.
Do not apply treatment only to visible spots; cover the required whole skin surface and reapply to hands if washed.
Persistent itch after treatment can be normal; new burrows or lesions and untreated contacts suggest reinfestation or failure.
Crusted scabies can be minimally itchy but has a very high mite burden and transmission risk.
Scabies is unrelated to poor hygiene and is not acquired from pets in ordinary human scabies.
Check age, pregnancy, breastfeeding and comorbidity before choosing topical or oral treatment.

Illustrations

Scabies lesions on the hand and finger web spacesClinical photograph showing small erythematous and excoriated scaly lesions across the palm, fingers and web spaces in scabies.Gzzz, Wikimedia Commons · CC-BY-SA-4.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.