Intense nocturnal itching should raise suspicion of scabies.

Alice S M Tidman, Michael J Tidman

The Practitioner 2013 May

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Scabies is caused by infestation with a parasitic mite Sarcoptes scabiei var hominis. The itch and rash appear to be largely the result of a delayed (type IV) allergic reaction to the mite, its eggs and excreta. Scabies is spread by a mite transferring to the skin surface of an unaffected person, usually by skin to skin contact with an infested person, but occasionally via contaminated bed linen, clothes or towels. In crusted scabies, mites are also dispersed within shed scales, enabling the condition to be contracted from contaminated surfaces. Patients with classical scabies usually present with an itchy non-specific rash. Often, the history alone can be 0032-6518 virtually diagnostic. An intense itch, affecting all body regions except the head, typically worse at night, appearing to be out of proportion to the physical evidence, with a close contact also itching, should prompt serious consideration of scabies. The generalised hypersensitivity rash consists of erythematous macules and papules with excoriation. Close inspection will reveal burrows usually up to 1 cm in length. The pathognomic sign of scabies is the presence of burrows. The crusted variant of scabies may not be itchy. It is characterised by areas of dry, scaly, hyperkeratotic and crusted skin, particularly on the extremities. Referral to secondary care should be considered in the following cases: diagnostic doubt; patient under two months of age; lack of response to two ourses of different insecticides; crusted scabies; or history suggests a isk of sexually transmitted infection. Outbreaks of scabies in institutions should be referred to the local health protection services.