Clinical Review

Scabies: diagnosis and treatment

BMJ 2005; 331 doi: http://dx.doi.org/10.1136/bmj.331.7517.619 (Published 15 September 2005) Cite this as: BMJ 2005;331:619
  1. Graham Johnston, consultant dermatologist (graham.johnston@uhl-tr.nhs.uk),
  2. Mike Sladden, specialist registrar in dermatology
  1. Leicester Royal Infirmary
  1. Correspondence to: G Johnston

    Introduction

    Scabies is an intensely itchy dermatosis caused by the mite Sarcoptes scabiei. A patient with ordinary scabies may have an average of 12 mites; however, those with crusted scabies may have thousands of mites. The infestation occurs at all ages, but particularly in children. It is a common public health problem in poor communities and is widespread in many underdeveloped countries.

    How is it spread?

    Scabies is highly contagious, and person to person spread occurs via direct contact with the skin. Transfer from clothes and bedding occurs rarely and only if contaminated by infested people immediately beforehand.1

    Infestation occurs when the pregnant female mite burrows into the skin and lays eggs. After two or three days, the larvae emerge and dig new burrows. They mature, mate, and repeat this cycle every two weeks.

    How do I diagnose it?

    A history of itching in several family members over the same period is almost pathognomonic. However, lack of a history of itching in family members does not exclude scabies. It can be notoriously difficult to get family members to admit to a history of possible scabies, and some people with scabies genuinely seem not to itch.

    If left untreated, scabies can continue for many months. It is important to remember that recurrence of symptoms after attempted treatment does not exclude the diagnosis of scabies because patients may not have treated themselves correctly or may have been reinfested by an untreated contact.

    What are the symptoms and signs?

    The main symptoms of scabies are probably a result of the host immune reaction to the burrowed mites and their products.2 Scabies presents within two to six weeks of initial infestation, but reinfestation can provoke symptoms within 48 hours. Pruritus is the hallmark of scabies regardless of age.

    Summary points

    A high index of suspicion is needed to diagnose scabies correctly

    Consider scabies in any adult with widespread eczema …

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