Scabies

🔍 When to Suspect

Intense itching that is characteristically worse at night, with a papular rash and possible mite burrows; a history of affected close contacts is highly suggestive

From the full topic in The Ocean Library: Scabies

🧭 When to suspect

Scabies is an infestation of the skin with the mite Sarcoptes scabiei var hominis. The cardinal symptom is intense itch (pruritus) that is characteristically worse at night, driven by a delayed (type IV) hypersensitivity reaction to the mite and its eggs and faeces. This is why, in a first infestation, symptoms typically take 3 to 6 weeks to appear – whereas on re-infestation they can develop within 1 to 3 days.

A history of itchy household, sexual or institutional contacts is highly suggestive. Crucially, absence of itch never excludes scabies – particularly in infants, the frail elderly, and those with cognitive impairment or neurological disease, in whom infestation may be silent. Scabies is a clinical diagnosis, usually confirmed by finding a burrow.

Two clinical priorities run through every consultation: recognise classical scabies and treat the patient with every contact simultaneously, and never miss crusted scabies in the at-risk patient. Rising UK incidence, real-world supply problems with topical scabicides, and emerging permethrin tolerance make accurate diagnosis and correct, co-ordinated treatment more important than ever.

Form	Key features	Notes
Classical scabies	Intense nocturnal itch; burrows and excoriated papules in finger webs, wrists, axillae, waist, genitals and buttocks	Only ~10–15 mites present; by far the most common form
Crusted (Norwegian) scabies	Thick, scaly, crusted plaques (may involve face and scalp); itch often mild or absent	Thousands of mites – highly contagious; immunosuppressed, elderly or frail; needs urgent specialist referral
Nodular scabies	Firm, very itchy reddish-brown nodules on the penis, scrotum, groin, axillae or buttocks	A hypersensitivity reaction to dead mites; can persist for weeks after cure and does not indicate active infection

Source: BASHH 2025 · British Association of Dermatologists

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