Scabies

How is a scabies infestation diagnosed?

Scabies is suggested by the presence of the typical rash and symptoms of unrelenting and worsening itch, particularly at night. Ultimately, the definitive diagnosis is made when evidence of mites is found from a skin scraping test. By scraping the skin (covered with a drop of mineral oil) sideways with a scalpel blade over an area of a burrow and examining the scrapings microscopically, it is possible to identify mites, eggs, or pellets. This process can be difficult, however, since burrows can be hard to identify. Sometimes scratch marks are mistaken for burrows, and even the examination of scrapings from 15 or more burrows may only reveal one or two mites or eggs. If the characteristic physical findings are present, scabies can often be treated without performing the skin scrapings necessary to identify the mites. Polymerase chain reaction (PCR) testing is available to identify the genetic material of the scabies mites when the diagnosis is difficult, though this is not generally used. The mites can also be identified in skin biopsies that are performed when other causes of skin disease are suspected.

Reviewed on 5/22/2014

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