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Scabies

Scabies Overview

  • Scabies is a contagious skin condition caused by a small mite.
  • The mite lays eggs in human skin, which hatch and grow into adult mites. This means that symptoms of the condition can last for months or even years.
  • Scabies causes generalized itching and is sometimes called the "seven year itch."
  • Skin lesions vary and may include short, linear, or nodular "burrows" between the fingers, tiny red bumps and blisters on the skin, or a widespread, crusted rash. Often, there are no visible skin lesions.
  • The mite is spread from person to person by skin-to-skin contact.
  • Animals can harbor a similar mite, but when the animal mite is passed to people, it cannot reproduce and dies within a few days.
  • Scabies can affect anyone, but it is particularly common in congested areas, such as nursing homes and hospitals, where it can spread widely.
  • In people who have poor immune systems or who are malnourished, scabies can cause a syndrome called "crusted scabies" or "Norwegian scabies," which is highly contagious and is associated with skin thickening and a scaly rash.

Scabies Causes

Scabies is caused by an eight-legged mite (Sarcoptes scabiei var. hominis) that is less than 0.5 mm long. How long do scabies live without a host? The mite can only survive for three days in the environment. Once on a human body, the mite may reproduce and cause symptoms for years.

The life cycle of the scabies mite starts when the female tunnels (burrows) into the skin and deposits her eggs. Larvae hatch from the eggs within three to 10 days and molt to become nymphs. Nymphs mature into adults that deposit additional eggs and live approximately four weeks. Burrowing and movement of the mites cause intense itching due to a type of allergic reaction to mite proteins. If the person has never been exposed to scabies before, he or she may not show symptoms until four to six weeks after the initial infestation. Individuals who have been exposed in the past usually show symptoms within a few days.

Where does scabies come from? Scabies is spread through skin-to-skin contact with a person who carries the mite. The mites often begin to cause symptoms first at the site where they enter the body. Thus, skin transmission during sexual intercourse may cause skin lesions on the penis, vaginal area, or groin. It is important to point out that scabies is not always a sexually transmitted disease (STD) and may be acquired through any skin-to-skin contact.

Less commonly, scabies infestation can happen through the sharing of clothes and bedding. Theoretically, a person can get scabies from touching something that the mite is on, but that is not a major mode of transmission. The mite only lives for two to three days away from human skin. Human scabies is not spread by contact with animals or pets.

Medically Reviewed by a Doctor on 7/7/2014

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Human scabies is an intensely pruritic skin infestation caused by the host-specific mite, Sarcoptes scabiei var hominis.

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