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Scabies is a skin condition characterized by a rash and intense itching. It is caused by mites getting under the skin's outer layer. The mites themselves are very small and cannot be seen with the naked eye.

How do I know if I have scabies?

Since you cannot see the mites, the rash and itching are the key features.

Scabies rash

The scabies rash typically affects the following skin surfaces: the hands, especially webbed skin between the fingers; skin folds at the wrists, knees, elbows, underarms, waist, or buttocks; the genitalia; the breasts, especially the dark area around the nipple; and the shoulder blades.

In adults and older children, the scabies rash often looks like tiny red bumps that are similar to small insect bites. In infants, the rash can appear as tiny fluid-filled blisters. The rash can extend to the neck, head, palms, and soles of the feet in babies who are younger than 2 years old.

In some cases, a person with scabies develops itchy skin nodules rather than a rash. These nodules can be up to 5 millimeters (1/4-inch) wide. They usually occur on skin that is covered by clothing, such as the trunk and upper legs.

Intense itching

Itching from scabies is often worse at night. It can involve any part of the skin, not just areas that have a rash or nodules.

Symptoms of scabies are part of the immune system's reaction to the scabies parasite and its waste products. This reaction usually takes a few weeks to develop in people who have never had scabies before. For this reason, people with their first episode of scabies may not develop an itchy rash until two to six weeks after the mites first burrow into the skin. However, in people who have had previous episodes of scabies, itching and rash often begin within one to four days.

Can scabies spread from person to person?

Scabies mites can be transmitted by direct skin-to-skin contact with an infected person, or by using clothing, blankets, sheets, towels, or furniture that has touched an infected person's skin. Scabies easily spreads during the close physical contact of sexual activity.

Scabies also can be passed from person to person in settings in which people live in close quarters, including hospitals, nursing homes, prisons, day-care centers, and homes. Anyone can catch scabies, including doctors, nurses, teachers, toddlers, and elderly people in wheelchairs. Having scabies is not a sign that someone is dirty, careless, or sexually promiscuous.

When a person catches scabies, pregnant female mites dig burrows in the skin and lay eggs along the way. After three to eight days, the eggs hatch and the young mites travel up the tunnels to the skin surface. There they grow to adulthood and mate, after which the females become pregnant and continue the skin infestation. Mite tunnels may be visible in the skin of a person who has scabies, although intense scratching often distorts their appearance.

Groups that are especially vulnerable to catching scabies include:

• people who have multiple sex partners
• anyone who lives in crowded conditions
• patients and health care workers in hospitals
• residents and caregivers in nursing homes
• students, teachers, and other caregivers in day-care centers
• people who live or work in institutions or prisons.

Diagnosing scabies

Scabies is a very contagious illness that can spread to members of your family and other people who have close physical contact with you. For this reason you should not try to self-diagnose this condition. You need to be examined by a professional.

After reviewing your symptoms and your risk factors (sexual contact, crowded living conditions, high-risk work environment), your doctor will examine your skin. Most often, the diagnosis is made based on skin findings and known exposure or possible exposure to scabies. The doctor looks for bumps between the fingers and toes and for burrows. The doctor also may scrape an area of rash gently to look for the mites or their eggs.

Treating scabies

Only prescription medications have been tested and approved to treat scabies in people. Topical permethrin cream applied to the skin is the usual first choice for treatment. Permethrin is a scabicide — an insecticide that kills scabies mites and eggs. Other medications are available, and your doctor may prescribe something other than topical permethrin depending on your age, medical history, coexisting skin conditions, and whether you are pregnant.

Scabies medications usually are applied from neck to toe after bathing, left on the skin for eight to 14 hours, and then washed off. In some cases, you may need to apply the medication a second time, depending on the type of medication used and your symptoms.

Ivermectin is an oral medication that also treats scabies effectively. It is taken as a single oral dose followed by a repeat dose two weeks later.

To help control itching, simple topical agents such as calamine lotion can be applied. If the itching keeps you awake, your doctor may suggest diphenhydramine (Benadryl) taken by mouth.

All sex partners, family members, and close contacts of someone with scabies should be treated for the infestation, even if they have no symptoms.

When will I get better from scabies?

With proper treatment, the rash and intense itching of scabies usually begin to subside within one to two days, although some milder itching can persist for a few weeks. In most cases, you stop being contagious within 24 hours.

Without treatment, scabies can be a long-term infestation that can spread to other people.

During the course of the illness, persistent scratching can lead to chronic crusting of the skin, or to painful secondary skin infections caused by bacteria.

Preventing scabies

To help prevent scabies:

• Avoid sharing clothing and towels.
• If your child goes to sleepover parties, provide a sleeping bag, pillow, and blanket from home.
• If someone in your household has been diagnosed with scabies, wash his or her clothing, bedding, and towels in hot water and dry these items in a hot dryer. This should kill all scabies mites and eggs. Clothing that cannot be washed should be sealed and stored for approximately one week, because scabies mites die within one to four days if not in contact with human skin.