Scabies

What is scabies?

Scabies is a mite infestation of the skin. The scabies mite, also known as the human itch or mange mite, causes intense itching, and it is contagious. 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 burrows to the skin surface. There they grow to adulthood and mate, after which the females become pregnant and continue the skin infestation. Once a female mite finishes laying her eggs, she spends the rest of her two-month lifespan at the deep end of her tunnel. Mite tunnels may be visible in the skin of a person who has scabies, although intense scratching often distorts their appearance.

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. However, scabies also can be passed from person to person in various nonsexual 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. Having scabies is not a sign that someone is dirty, careless, or sexually promiscuous.

Worldwide, it's estimated that more than 400 million new cases of scabies occur each year in men, women, and children of all ages and races. 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 and nursing homes
students, teachers, and other caregivers in day-care centers
people who live or work in institutions or prisons.

Symptoms of scabies

Symptoms of scabies include:

Intense itching: This itching is often worse at night, and it can involve any part of the skin, not just areas that have rash or nodules.
A 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, it can appear as tiny vesicles (small fluid-filled blisters). Also, the rash can extend to the neck, head, palms, and soles of the feet in babies who are younger than 2 years old.

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Red or brown nodules (larger skin bumps): In some cases, a person with scabies develops skin nodules rather than a rash. These tiny nodules can be up to 5 millimeters (0.2 inch) wide, and they usually occur on skin that is covered by clothing, such as the trunk and upper legs.

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 skin infestation starts. However, in people who have had previous episodes of scabies, the body's reaction is triggered sooner, so itching and rash often begin within one to four days.

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 never self-diagnose this illness. You must 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.

Expected duration of 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.

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 at least 72 hours, because scabies mites die within one to four days if not in contact with human skin.

Treating scabies

Topical permethrin (Nix, Elimite) is usually the first choice for treatment. Other topical options for treatment include benzyl benzoate, sulfur ointment, spinosad (Natroba), and ivermectin (Sklice, Soolantra). Ivermectin (Stromectol) is also available as an oral medication and may be recommended if oral treatment is preferred or if permethrin causes side effects.

The choice of an alternative to permethrin depends on a number of factors, including a person's age, pregnancy, the presence of coexisting skin conditions, medication cost, and medical history. For example, ivermectin is not recommended during pregnancy due to risks to the fetus.

To help control itching, simple topical agents such as calamine lotion can be applied. If the itching keeps you awake, an antihistamine such as diphenhydramine (Benadryl) may be recommended.

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 to call a professional

Call your doctor if you have symptoms of scabies or if you have been exposed to someone with scabies.

Also, contact your doctor if you have been diagnosed with scabies and your symptoms have not improved significantly within one week after completing treatment.

Prognosis

If you follow your doctor's directions for using scabies medication, the prognosis is excellent. In most cases, you stop being contagious within 24 hours, and your symptoms should improve noticeably within two days.