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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Sarcoptes scabiei mite — prolonged skin-to-skin contact. NOT a sign of poor hygiene
- Intense nocturnal pruritus. Burrows in finger web spaces, wrists, axillae, genitalia
- Diagnosis: clinical. Dermoscopy (delta-wing jet sign) or skin scraping
- Permethrin 5% cream: whole body neck down, leave 8-12 hours, repeat in 7 days
- Treat ALL household contacts simultaneously — even if asymptomatic
Overview
Scabies is caused by the mite Sarcoptes scabiei var. hominis burrowing into the stratum corneum. Incubation 4-6 weeks for primary infection. Symptoms are from type IV hypersensitivity to mite products. Crusted (Norwegian) scabies in immunocompromised has thousands of mites and extreme transmissibility.
Epidemiology
Affects ~200 million worldwide. Common in UK — outbreaks in care homes and crowded settings. All ages and social classes. NOT related to hygiene.
Clinical Features
Symptoms
Intense pruritus — characteristically worse at night
Other household members/contacts affected
Widespread crusted plaques with minimal itch (crusted scabies — immunocompromised)
Signs
Linear burrows in finger web spaces, wrists, axillary folds, areolae, genitalia
Papular excoriated rash — widespread
Genital nodules in males
Infants: face, palms, soles may be involved
Crusted (Norwegian) scabies: thick hyperkeratotic crusts — extremely contagious
Investigations
First-line
Clinical diagnosisNocturnal itch + burrows + contacts affected
DermoscopyDelta-wing jet sign (mite head) — confirmatory
Second-line
Skin scrapingKOH microscopy — mites, eggs, or scybala
Management
NICE CKS — Scabies + BAD Guidelines1
Permethrin 5% cream
- Apply ENTIRE body neck down (include scalp/face/ears in elderly)
- Leave 8-12 hours, wash off. REPEAT in 7 days
- Pay attention to web spaces, under nails, wrists, groin
2
Alternative
- Malathion 0.5% aqueous lotion: apply 24 hours, repeat day 7
3
Contacts and decontamination
- ALL household contacts treated SIMULTANEOUSLY — even if asymptomatic
- Wash bedding/clothing at >=60°C on treatment day
- Items that cannot be washed: seal in bag for 72 hours
4
Persistent itch / resistant cases
- Itch may persist 2-4 weeks AFTER successful treatment (allergic response)
- Treat with emollients, crotamiton, sedating antihistamines
- If confirmed re-infestation: oral ivermectin 200 mcg/kg, repeat day 7
Complications
- Secondary infection: Excoriation leading to impetigo, cellulitis
- Post-scabies itch: Persistent weeks after treatment — not treatment failure
- Crusted scabies outbreaks: In care homes — extreme infectivity
UKMLA Exam Tips
- 1Nocturnal itch + burrows in web spaces + contacts affected = SCABIES
- 2Permethrin 5%: TWO applications, 7 days apart. WHOLE body neck down
- 3Treat ALL contacts SIMULTANEOUSLY — even if asymptomatic
- 4Post-treatment itch 2-4 weeks = normal allergic response, NOT treatment failure
- 5Crusted scabies: immunocompromised + minimal itch + HIGHLY contagious
practicetest your knowledge on scabiesApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — dermatology and beyond.
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