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Scabies - including symptoms, treatment and prevention

A picture of a Sarcoptes scabiei (scabies mite)Scabies is an infestation of the skin caused by the scabies mite Sarcoptes scabiei (see image). The mite is very tiny, 0.2 mm to 0.4 mm long, and cannot easily be seen without magnification. It occurs worldwide and in all races and social classes. Scabies is not an indication of poor hygiene.

How scabies is spread

Scabies is usually transmitted by direct skin-to-skin contact, or rarely, by underwear or bed clothes that have been freshly contaminated by an infested person. The mites can survive for only a few days off the human or animal body.

Signs and symptoms

little red lumps on a handScabies and other mites usually infest the skin especially where there are creases, such as:

  • between the fingers (see images)
  • on the front of the wrists
  • in the folds of the elbows, armpits and buttocks
  • genitals.

When mites have been transmitted from animals (such as dogs) to people, the mites are commonly found on areas of skin having contact with the animal, Scabieincluding forearms, chest and neck. However, mites from animals cannot breed on humans, so do not cause ongoing infestation. Scabies mites cause intense itching, especially at night. Thread-like ‘tunnels’, about 10 mm long, may be visible as grey lines in the skin, but they are often difficult to detect. Scabies infection may appear on the genitals as small itchy lumps.

Diagnosis

Scabies and other mites that cause skin disease are diagnosed by examining skin scrapings with a microscope.

Incubation period

(time between becoming infected and developing symptoms)

Itching begins 2 to 6 weeks after infestation in individuals not previously exposed to scabies and within 1 to 5 days in individuals previously exposed.

Infectious period

(time during which an infested person can transmit the infestation to others)

Until the mites and eggs are destroyed by treatment. People can be infectious even before the itching begins.

Treatment

Skin disease caused by mites can easily be confused with other skin diseases. Treatment should not be undertaken until the diagnosis has been confirmed by a doctor, following examination of skin scrapings for mites. This is particularly important for babies, pregnant women or people who already have other forms of skin disease. Babies under 12 months of age need special treatment. Treatment involves application of insecticidal cream, lotion or solution as prescribed by a doctor. For see the Direction for the application of a topical scabicide (PDF 59KB) for detailed information on what you should do and how to apply topical scabicides.

Prevention

  • Exclude people with scabies from childcare, preschool, school and work until one day after treatment commences.
  • All close (skin-to-skin) contacts and other people in the same household should be treated at the same time, even if no itching or other symptoms are present. By the time scabies is diagnosed in one person, many other people may have been infested. If everyone is not treated at the same time, treatment is likely to be unsuccessful.
  • Underwear, clothing, towels, bed linen and personal effects such as slippers, bed jackets, dressing gowns and knee rugs used by the affected person in the 72 hours prior to treatment should be laundered using a hot wash cycle (hotter than 50°C) or hot tumble dried to kill the mites. If items are unable to be laundered or hot tumble dried, place them in a sealed plastic bag and leave them for 72 hours before airing and reusing.
  • Mattresses and upholstered furniture can be vacuumed or gently ironed.

Useful links


Image 2 and 3 - Scabies (Sarcoptes scabiei var. hominis). Image courtesy of Public Health Image Library (PHIL), Department of Health and Human Services, Centers for Disease Control and Prevention (CDC-USA)

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