What is scabies?

Scabies is a contagious, intensely itchy, skin disease caused by a mite (Sarcoptes scabiei), which is becoming increasingly common for reasons that are unknown.

Scabies spreads from person to person usually by close skin-to-skin contact or shared clothing or bed linen.

It is now accepted that mites can spread when a non-infected person stands too close to an infected person. Mites are 0.1mm in diameter.

What is the Causes of Scabies

Scabies mites are attracted to the warmth and smell of humans. Female mites burrow into the skin, creating small, threadlike tunnels that you can sometimes see. The mites lay eggs and leave feces in these tunnels.

How scabies is spread1

  1. Scabies usually is spread by close, intimate contact, such as sleeping in the same bed with or touching someone who has scabies. The scabies mite cannot fly or jump, and it moves very slowly.
  2. Scabies mites can live up to 36 hours without a human host. During this time, the mites may spread to other people. Mites usually spread through skin-to-skin contact, but they can spread from contact with clothing, bed linens, and other household and personal items.
  3. A mite burrows very quickly under the skin, especially in areas where it is rough or wrinkled, such as the elbows, knuckles, and knees. Touching or scratching an area that is infested with mites can spread them to other parts of the body.
  4. After burrowing under the skin, a female mite lays 10 to 25 eggs before she dies. The eggs hatch into larvae 2 to 3 days later. These larvae move to the skin's surface and become adults within about 14 to 17 days. This cycle continues until the mites are killed.

The scabies mite that infests humans does not live on dogs or other pets. Similarly, animal-transmitted scabies mites do not survive or reproduce on humans. However, they can live long enough on humans to cause itchy hives or raised bumps that last a few days.

Contagious and incubation periods

Scabies is contagious. If you have scabies, you can spread mites to other people before and after you develop symptoms, for as long as you remain infested and untreated. After your first infestation, several weeks may pass before you develop symptoms. You are contagious during this time, which is known as the incubation period.

If you ever become infested with mites again, it will likely take only 2 or 3 days for you to develop symptoms.

What is the treatment for a scabies infestation?

Curing scabies is rather easy. Steps that should be taken include:

  1. Apply a mite-killer like permethrin (Elimite). These creams are applied from the neck down, left on overnight, then washed off. This application is usually repeated in seven days. An alternative treatment is 1 ounce of a 1% lotion or 30 grams of cream of lindane, applied from the neck down and washed off after approximately eight hours. Since lindane can cause seizures when it is absorbed through the skin, it should not be used if skin is significantly irritated or wet, such as with extensive skin disease, rash, or after a bath. As an additional precaution, lindane should not be used in pregnant or nursing women or children younger than 2 years old. Lindane is only recommended if patients cannot tolerate other therapies or if other therapies have not been effective.
  2. An oral medication, ivermectin, is an effective scabicide that does not require messy creams to be applied. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than application of the cream, ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be superior to permethrin in eradicating scabies.
  3. Antihistamines, such as diphenhydramine (Benadryl), can be useful in helping provide relief from itching.
  4. Wash linens and bedclothes in hot water. Because mites don't live long away from the body, it is not necessary to dry-clean the whole wardrobe, spray furniture and rugs, and so forth.
  5. Treat sexual contacts or relevant family members (who either have either symptoms or have the kind of relationship that makes transmission likely).

Just as the itch of scabies takes a while to reach a crescendo, it takes a few days to subside after treatment. After a week or two, relief is dramatic. If that doesn't happen, the diagnosis of scabies must be questioned.