Clinical Features:
When a person is infested with scabies mites for the first time, there is usually little evidence of infestation for the first month (range 2 to 6 weeks).  After this time and in subsequent infestations, people usually become sensitized to mites and symptoms generally occur within 1 to 4 days.  Mites burrowing under the skin cause a rash, which is most frequently found on the hands, particularly the webbing between the fingers; the folds of the wrist, elbow or knee; the penis; the breast; or the shoulder blades.  Burrows and mites may be few in number and difficult to find in some cases.  A papular "scabies rash" may be seen in skin areas where female mites are absent, usually on the buttocks, scapular region and abdomen; this may be a result of sensitization from a previous infection.  Most commonly there is severe itching, especially at night and frequently over much of the body, including areas where mites are undetectable.  A more severe form of scabies that is more common among immunocompromised persons is called Norwegian scabies, characterized by vesicles and formation of thick crusts over the skin, accompanied by abundant mites but only slight itching.  Complications due to infestation are usually caused by secondary bacterial infections from scratching.

Laboratory Diagnosis:
Most diagnoses of scabies infestation are made based upon the appearance and distribution of the rash and the presence of burrows.  Whenever possible scabies should be confirmed by isolating the mites, ova or feces in a skin scraping.  Scrapings should be made at the burrows, especially on the hands between the fingers and the folds of the wrist.  Alternatively, mites can be extracted from a burrow by gently pricking open the burrow with a needle and working it toward the end where the mite is living.

Diagnostic findings

• Microscopy

Treatment:
Several lotions are available to treat scabies.  The treatment of choice is the topical use of permethrin (5%).  Crotamiton and ivermectin* are alternative drugs.  Ivermectin* is taken orally and is effective for treating crusted scabies in immunocompromised persons.  If a topical preparation is used, a second treatment with the same product may be necessary 7-10 days later.  All clothes, bedding, and towels used by the infested person during the 2 days before treatment should be washed in hot water, and dried in a hot dryer.  For additional information, see the recommendations in The Medical Letter (Drugs for Parasitic Infections).

* This drug is approved by the FDA, but considered investigational for this purpose.