Scabies

Topic Overview

What is scabies?

Scabies is a very itchy skin condition caused by tiny mites that burrow into your skin. See a picture of scabies .

Scabies can affect people of all ages and from all incomes and social levels. Even people who keep themselves very clean can get scabies.

How is scabies spread?

Scabies mites spread by close contact with someone who has scabies. Scabies can also be spread by sharing towels, bed sheets, and other personal belongings.

Scabies often affects several family members at the same time. You can spread it to another person before you have symptoms.

What are the symptoms?

Scabies causes severe itching that is usually worse at night. Small children and older adults tend to have the worst itching. Children typically have worse skin reactions.

If this is the first time you have had scabies, it may be several weeks before you have itching and skin sores. But if you have had it before, symptoms will probably start in a few days.

How is scabies diagnosed?

A doctor can usually diagnose scabies based on your symptoms. Scabies is especially likely if you have had close contact with other people who have had similar symptoms.

Sometimes a doctor confirms a diagnosis by looking for signs of mites on a sample of your skin. The doctor gently scrapes some dry skin from an affected area and then looks at it under a microscope. This test is not painful for most people.

How is it treated?

Scabies will not go away on its own. You need to use a special cream or lotion that a doctor prescribes. In severe cases, your doctor may also give you pills to take.

Some scabies medicines are not safe for children, older adults, and women who are pregnant or breast-feeding. To avoid dangerous side effects, be sure to follow your doctor's instructions carefully.

If you have scabies, you and anyone you have close contact with must all be treated at once. This keeps the mites from being passed back and forth from person to person. You must also carefully wash all clothes, towels, and bedding.

After treatment, the itching usually lasts another 2 to 4 weeks. It will take your body that long to get over the allergic reaction caused by the mites. If you still have symptoms after 4 weeks, you may need another treatment.

Frequently Asked Questions

Cause

Scabies is caused by the mite Sarcoptes scabiei. 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

• 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.
• 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.
• 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.
• 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.

Symptoms

If you have scabies, you will likely have itching and irritated skin that gets worse until the mites are killed.

• Itching usually starts first. It often becomes noticeable at night or after bathing and is sometimes mistaken for dry skin. Itching is caused by an allergic reaction to the scabies mite. Sometimes the itching is very intense, especially in small children and older adults.
• Irritated skin often appears as a rash and skin sores that look like tiny curving tracks. These symptoms are a result of the mite tunneling under the upper layers of the skin. Sometimes you can see a small blister or the mite itself, which looks like a tiny black dot, at the end of a burrow. The tracks may be difficult to see after you scratch the area. Babies may only have red and inflamed skin, sometimes with small blisterlike sores.

Symptoms are most likely to develop:

• Between the fingers and on the palm side of the wrists.
• On the outside surfaces of the elbows and in the armpits.
• Around the waistline and navel.
• On the buttocks.
• Around the nipples, bra line, and the sides of the breasts (in women).
• On the genitals (in men).

In babies and small children, itching and skin irritation may also occur:

• Around or on the scalp, neck, and face.
• On the palms of the hands and soles of the feet. Often the first symptom noticed in babies is a series of tiny blisterlike sores (vesicles) in these areas.

Other problems

Skin sores, called secondary lesions, can develop later in the course of the condition. Problems may include:

• Scratches, sometimes covered by a crust. Scratching the scabies burrows can irritate and break open the skin.
• Red, dry, scaly, irritated areas of skin.
• Nodular scabies. These are small reddish brown raised areas (nodules). The nodules may develop in covered areas such as the armpits, groin, buttocks, scrotum, and penis. The nodules itch and may persist for weeks or months after scabies has been cured.

Babies and older adults are especially at risk for these lesions because they may not be treated right away. Early symptoms in babies and older adults are more likely to be missed or mistaken for another condition.

What Happens

First-time infestation

The first time you are infested with the scabies mite, itching may not begin for several weeks. During this time, you are contagious but may not know that you are carrying scabies mites.

In the first few weeks of scabies infestation, the body develops sensitivity to the mites, their eggs, and their feces. Once your body has become sensitized, an allergic reaction is triggered, causing itching. With treatment, the scabies mites die and the itching gradually goes away over a period of days to weeks. Usually a doctor will tell you it is safe for your child to return to school after treatment is completed and the medication has been washed from the skin. Treatment takes 1 to 3 days depending on the medication used.

If all of the scabies eggs are not killed by the first treatment, they may hatch and cause symptoms again. Without treatment, the mites reproduce and cause more sores and more itching. Scabies will not go away on its own. Only animal-transmitted scabies will go away without treatment.

Repeat infestation

If you have had scabies and are infested with the mites again, itching will begin almost immediately. The allergic sensitivity developed during the previous exposure triggers an immediate reaction to the mites. Treatment is usually required to kill the mites and eggs; on rare occasions, a person's allergic reaction will kill the scabies.

Complications

The most common complication of scabies is a bacterial skin infection, such as impetigo. This most often occurs when the skin has been scratched raw. Hair follicles may also become infected (folliculitis). Antibiotics may be needed to treat a bacterial skin infection.

The skin can become thick, red, and scaly or shiny from persistent scratching.

In rare cases, crusted (Norwegian) scabies, a severe form of scabies, develops. Usually, this type of scabies is most common in people who have weakened immune systems, such as those with HIV. People with crusted scabies may have extreme infestations with tens of thousands of mites; in otherwise healthy people, an infestation is usually limited to about 10 or 15 mites.²

What Increases Your Risk

The following groups of people are at higher risk of exposure to scabies mites:

• Sexually active young adults. Close skin-to-skin contact (not specifically sexual intercourse) makes transmission of the scabies mites more likely.
• People who live or work in institutions such as nursing homes, homes for the developmentally disabled, and prisons.
• People who live in crowded conditions.
• Children from developing countries.

People who have weakened immune systems, such as HIV, and those who are unable to communicate about their physical symptoms are at risk for developing severe, difficult-to-treat cases of scabies, particularly crusted (Norwegian) scabies.

When To Call a Doctor

Call your doctor if:

• Family members suddenly develop severe nighttime itching that does not go away in 3 to 4 days.
• You develop serious side effects from any product used to treat scabies.
• Itching lasts longer than 4 weeks after treatment. (After successful treatment, itching will usually last for 2 to 4 weeks as a result of the allergic reaction to previous mite bites.)
• You develop signs of a skin infection. These may include:
  • Increased pain, swelling, heat, redness, or tenderness.
  • Red streaks extending away from the affected area.
  • Continued discharge of pus.
  • Fever of 100 °F (37.8 °C) or higher with no other cause.

Watchful Waiting

Do not wait longer than 3 to 4 days to seek medical attention if you think you have scabies. The infestation and symptoms will not go away without treatment. The longer you wait to seek care, the more likely you are to spread the mites to other people.

If you are certain that a case of scabies is related to a similar condition spread by animals (sarcoptic mange), it may be appropriate to wait as long as a week. The mites that cause this type of scabies cannot live on human skin for more than a few days, so the human infestation should go away on its own without treatment. The animal, however, must be treated by a veterinarian.

Who To See

The following health professionals can diagnose and treat scabies:

• Local health department staff
• Family medicine doctor or internist
• Nurse practitioner
• Physician assistant
• Pediatrician
• Dermatologist

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

Usually, your doctor can diagnose scabies if you have:

• Severe itching, especially at night.
• A rash, sometimes with skin sores . These may look like tiny curving tracks. Sometimes you may have a small blister or see a tiny black dot at one end of the track. In babies, the tracks may look like generally red and inflamed skin, sometimes with small blisterlike sores. Your doctor will check your skin for sores, scratches, raw areas, scabs, or red skin that are typical of scabies infestation.
• Other family members or people you are physically close with who are also itching or who have recently been diagnosed with scabies.

Sometimes, you may need one of the following tests to confirm the diagnosis:

• Skin scrapings. Your doctor collects material from the itchy area by applying a drop of mineral oil or other liquid to the skin and then scraping the area with a scalpel. He or she then examines the scrapings under a microscope to look for scabies mites, eggs, egg casings, or feces. This is the most common test used to diagnose scabies.
• Ink test or ink burrow test. Your doctor strokes a washable felt-tip pen across the itchy areas. The surface ink is wiped off with water or an alcohol swab. Any burrows present will absorb the ink and be seen as a dark line.
• Skin biopsy/punch biopsy. A skin sample (punch biopsy or shave biopsy) may be helpful in diagnosing difficult-to-diagnose conditions. Skin biopsy is rarely used.
• Needle extraction of the mite. On rare occasions, a needle is used to remove a mite from the burrow. The mite is placed on a slide and examined under a microscope.

Treatment Overview

If you suspect that you have scabies, see your doctor as soon as possible for treatment. Delaying treatment increases the risk that the scabies mites will spread to other people. Scabies will not go away on its own.

• Scabies can only be cured with prescription creams or lotions. Nonprescription medicines are not strong enough to kill the mites.
• Most creams or lotions are applied to the entire body from the neck down. On infants, the medicine is also applied to the scalp, face, and neck, taking care to avoid the area around the mouth and eyes. The medicine usually is left on for 8 to 14 hours and then washed off.
• Children can usually return to day care or school after treatment is completed and the medicine has been washed off. Treatment takes 1 to 3 days depending on the medicine used.
• Your health professional may recommend that you be examined 2 weeks and 4 weeks after completing treatment to ensure that the scabies has cleared up.
• Persistent nodular scabies may be treated with injections of steroids into the nodules. In rare cases, coal tar products are applied to the nodules.

You will likely continue to itch for days to weeks after having successfully killed the mites. This itching is caused by an ongoing allergic reaction to the mite bites. Your doctor may recommend antihistamines (such as Benadryl), steroid creams, and, in severe cases, steroid pills to help relieve itching. The allergic reaction will usually disappear gradually.

Who else should be treated?

Anyone who has had close physical contact with a person who is infested with scabies should be treated. This may include several members of the same household, including anyone who has prolonged skin-to-skin contact (sleeping, bathing, or holding hands) with the infected person.

Prevention

Avoiding close skin-to-skin contact with someone who has scabies, as well as with their personal items, will help you avoid getting scabies. People who have scabies are encouraged to use care to avoid spreading the mites to others.

Home Treatment

All people in the household who have had close skin-to-skin contact with a scabies-affected person during the past month must be treated. This usually includes everyone in the home, even if they don't have symptoms. (Symptoms can take 4 to 6 weeks to develop after a person is infested.)

It is important to treat the bedding and clothing of the affected person to destroy any live scabies mites as soon as prescription treatment begins.

Nonprescription medicine for scabies mites

There is no over-the-counter medicine that can cure a scabies infestation. Over-the-counter lice medicines are not strong enough to kill scabies mites. If you think you have scabies, do not use nonprescription products before seeing your doctor because doing so could make it difficult to diagnose your condition.

Nonprescription medicine for itching

You can use one of the following over-the-counter medicines to help relieve itching from scabies:

• Oral antihistamines (such as Benadryl). These medicines will not interfere with the diagnosis or treatment of scabies. Don't give antihistamines to your child unless you've checked with the doctor first.
• Corticosteroid creams (such as hydrocortisone cream). This type of medicine may make the scabies sores look different and make it harder for your doctor to diagnose the problem. Only use this medicine after your doctor has seen and diagnosed your condition.

Medications

Prescription permethrin (Elimite) cream or lotion is the most commonly used medicine to treat scabies. Unlike the more toxic lindane, permethrin is considered safe for infants as young as 2 months old.

• Only permethrin, crotamiton, and sulfur ointment are considered safe for treating children younger than age 2.
• Lindane is sometimes used as a secondary treatment for a defined group of people. It must only be used as a single application exactly as directed. Lindane is not recommended for babies, older adults, anyone who weighs less than 110 lb (49.9 kg), or people who have a weakened immune system.³ Lindane should also not be used for people who have widespread dermatitis or women who are pregnant or breast-feeding.⁴ Lindane shampoo and lotion are not available in California for treating lice or scabies.⁵
• Crusted (Norwegian) scabies (rare) often requires multiple treatments, sometimes with more than one medicine.
• Steroid creams, antihistamines (such as Benadryl), and, in severe cases, steroid pills can be used to relieve itching, but they do not kill scabies mites. Don't give antihistamines to your child unless you've checked with the doctor first.
• Persistent nodular scabies may be treated with injections of steroids into the nodules or (rarely) with coal tar products applied to the skin.

Most creams or lotions are applied to the entire body from the neck down. On infants, the medicine is also applied to the scalp, face, and neck, taking care to avoid the area around the mouth and eyes. The medicine usually is left on for 8 to 14 hours and then washed off.

Nonprescription medicines are not strong enough to kill the scabies mites .

Medication Choices

Prescription medicines used to treat scabies include:

• Permethrin cream 5% (Elimite), a standard first treatment for scabies. It usually cures scabies infestation after the first application.
• Lindane 1% (Kwell), which must be used exactly as directed to avoid dangerous side effects. Lindane is only used if your scabies persists after trying other medications or you are unable to use other treatments.⁶
• Sulfur ointment (precipitated sulfur) 5% to 10%, a milder and less effective medicine than permethrin or lindane, is sometimes used to treat infants and pregnant or breast-feeding women.
• Crotamiton 10% (Eurax), which is not often used to treat scabies because it does not dependably kill all the mites and their eggs.
• Ivermectin, an oral medication. Currently in the United States, treating scabies with ivermectin is considered an off-label use. More research is needed to confirm its effectiveness and to determine which people would benefit most from its use.² However, a doctor may prescribe it in certain situations, such as in combination with other medicines to treat people with severe cases of scabies.

You may also need to take an antibiotic if you develop a secondary skin infection.

What To Think About

When used correctly, lindane is considered a safe and effective treatment for scabies. With incorrect use or overuse, however, lindane can be dangerous and can permanently damage the central nervous system. If your doctor prescribes lindane to treat scabies, make sure you receive, understand, and follow detailed instructions for using it correctly.

Scabies treatment can fail:

• When the medicine is not applied properly. Carefully follow instructions for using scabies medications.
• If the medicine does not kill the scabies eggs. When the eggs hatch, a new infestation begins.
• When other members of the affected person's household are not treated.

Surgery

Surgery is not an appropriate treatment for scabies.

Other Treatment

There is no other treatment for scabies at this time.

References

Citations

1. Chosidow O (2006). Scabies. New England Journal of Medicine, 354(16): 1718-1727.

2. Mathieu ME, Wilson BB (2005). Scabies. In GL Mandell et al., eds., Mandell, Douglas, and Bennett's Principles and Practices of Infectious Diseases, 6th ed., chap. 292, pp. 3304-3307. Philadelphia: Elsevier Churchill Livingstone.

3. U.S. Food and Drug Administration (2003). FDA issues health advisory regarding labeling changes for lindane products. FDA Talk Paper T03-19. Available online: http://www.fda.gov/bbs/topics/ANSWERS/2003/ANS01205.html.

4. Centers for Disease Control and Prevention (2006). Sexually transmitted diseases treatment guidelines, 2006. MMWR, 55(RR-11): 79-80.

5. Stone SP (2003). Scabies and pediculosis. In IM Freedberg et al., eds., Fitzpatrick's Dermatology in General Medicine, 6th ed., vol. 2, chap. 238, pp. 2283-2289. New York: McGraw-Hill.

6. U.S. Food and Drug Administration (2003). FDA Public Health Advisory: Safety of Topical Lindane Products for the Treatment of Scabies and Lice. Available online: http://www.fda.gov/cder/drug/infopage/lindane/lindanePHA.htm.

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