FFinalistSouthampton · 2027
Dermatology
AKT · Dermatology/Infections & infestations

Scabies

Sarcoptes scabiei mite — burrows in the stratum corneum

Overview

An intensely itchy infestation by the Sarcoptes scabiei mite, which burrows in the stratum corneum. Severe itch worse at night, burrows in the finger web-spaces, and affected household contacts are the triad. Crusted (Norwegian) scabies is a hyperinfestation in the immunosuppressed/elderly.

Recognise

  • Intense generalised itch, classically WORSE AT NIGHT, often sparing the head in adults
  • Linear/serpiginous burrows in the finger web-spaces, wrists, and genitalia (penile/scrotal papules); a secondary widespread eczematous/papular id reaction
  • Itchy household/sexual contacts (the mite spreads by prolonged skin contact)

Red flags

  • Crusted (Norwegian) scabies — thick hyperkeratotic crusts teeming with mites, often minimal itch, highly contagious, in the immunosuppressed/elderly → isolate and treat aggressively

Differentials & how to tell them apart

Atopic eczemaflexural, atopy history, no burrows and contacts not itchy
Dermatitis herpetiformisgrouped vesicles on extensors, coeliac association, IgA on biopsy
Papular urticaria/insect bitesgrouped urticated papules, no web-space burrows
Contact dermatitisconfined to the contact site, no nocturnal itch or burrows

Clinical image

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Scabies — clinical imagesDermNet

Investigations

Clinical (burrows + itch + contacts). Dermoscopy or skin scraping can show the mite ("delta-wing/jet-trail" sign) if confirmation is needed.

Management

Permethrin 5% cream to the whole body, repeated after 7 days, + treat all contacts simultaneously

  1. 1Permethrin 5% cream applied to the whole body (neck-down in adults, include head in infants/elderly), washed off after 8–12 hours and REPEATED after 7 days.Gate: Treat ALL household members and sexual/close contacts at the SAME TIME — even if asymptomatic — and decontaminate bedding/clothing/towels (wash at ≥60°C or seal in a bag); failing to treat contacts is the commonest cause of "treatment failure"
  2. 2Persistent itch for up to 4–6 weeks after successful treatment is normal (treat with emollient/antihistamine/mild steroid, not repeat scabicide). Crusted scabies → isolate, oral ivermectin ± topical, specialist input.
Permethrin 5% cream — first-line — apply to the WHOLE body, wash off after ~8–12h, REPEAT after 7 days
Malathion 0.5% aqueous lotion — second-line / if permethrin unsuitable
Oral ivermectin — crusted scabies, outbreaks, or when topical treatment is impractical (specialist)
Antihistamine / mild topical steroid — for the itch, which persists for weeks after successful treatment

Key points

Post-scabetic itch lasting weeks is NOT treatment failure — do not keep re-applying permethrin. The diagnosis is often made on the combination of nocturnal itch + web-space burrows + itchy contacts.

Monitor & prognosis

Itch settling over weeks; recurrence implies untreated contacts/re-infestation.

Cured by correctly applied treatment of patient + contacts.

Source: NICE CKS Scabies; DermNet