Scabies

Scabies Overview

  • Scabies is a contagious skin condition caused by a small mite (Sarcoptes scabiei var. hominis).
  • The mite lays eggs in human skin, which hatch and grow into adult mites. This means that signs and symptoms of the skin condition can last for months or even years.
  • Symptoms and signs of scabies include generalized intense itching; the condition is sometimes called the "seven year itch."
  • Symptoms and signs of scabies on the skin 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.
  • The United States Centers for Disease Control and Prevention (CDC) recommends that only prescribed medications be used to treat scabies.
  • The majority of uncomplicated scabies infections are treated by primary-care providers or pediatricians.
  • 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.

What Is Scabies?

Scabies is a disease characterized by severe itchy skin and a reddish rash that is contagious from person to person. It is caused by a mite (Sarcoptes scabiei var. hominis) that burrows into the skin. Although it can be transmitted by sexual contact, there is controversy about labeling it a sexually transmitted disease (STD or STI) because it can also be transmitted by nonsexual physical contact.

What Causes Scabies?

Scabies is caused by an eight-legged mite (Sarcoptes scabiei var. hominis) that is less than 0.5 mm long. Worldwide, about 300 million people are infected each year. In the U.S., there were outbreaks of scabies in 10 schools in Texas and in hospital workers in Charlotte, N.C., in 2015.

What Are Risk Factors for Scabies?

The highest risk factor for scabies is skin contact with a person with scabies. Transmission of the infection during sex is very common. Also included is physical contact (nonsexual) with an infected person or items that have been in contact with the skin of an infected person (for example, clothing, towels, bedding, or even items like chairs or couches). These nonsexual contacts are how one person may infect other family members, such as a baby or child. However, people with STDs are at risk to become infected and then harm the health of others by both sexual and nonsexual transfer of the mite.

Nonsexual outbreaks can occur. For example, an outbreak occurred in an El Paso, Texas, child care facility and three health care facilities in Dayton, Ohio, in 2017.

What Is the Life Cycle of the Scabies Mite?

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.

Learn how to treat and prevent scabies.

Scabies Treatment and Prevention

If a household member becomes infested with scabies, the goal of treatment (for example, with a mite-killer such as permethrin [Elimite] or lindane [Kwell]) is also to prevent infestation of household contacts. Therefore, treatment is usually recommended for all close contacts of the affected person. The treatment should occur for the affected individual and his/her close contacts at the same time in order to prevent re-exposure. Permethrin can be used on infants 2 months and older; lindane is not recommended for use in children.

How Long Do Scabies Live Without a Human Host?

The mite can only survive for three days in the environment. Once on a human body, the mite may reproduce; if the infection remains untreated, it can cause symptoms for years.

Where Does Scabies Come From?

Scabies is spread (transmitted) 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. However, in young, sexually active individuals, scabies is usually spread by sexual 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; however, the human mites may infest pets like dogs and cats and cause itching; the human mites do not multiply on pets and quickly die. The mites that cause sarcoptic mange, or dog or pet scabies, only multiply on pets like dogs and cats; although they may cause itching on humans, they do not multiply on humans and soon die.

What Are Scabies Symptoms and Signs? What Do Scabies Skin Lesions Look Like?

Symptoms occur from two to six weeks to appear after exposure. They include severe and continuous itching, especially at night.

  • The skin may show signs of small insect-type bites, or the lesions may look like pimples, bumps, or blisters, especially around the wrist, elbow, knee, underarm area, groin, or finger webs. The skin may also have redness, rash, or have sores (welts, bumps or nodules, especially in children, termed nodular scabies) due to scratching of the area. Large nodules of 2-20 mm in diameter may appear in infants unable to scratch.
  • A burrow (a short S-shaped track that indicates the mite's movement under the skin) may also be visible, especially in the webs of fingers and toes. Burrows may be small enough to be overlooked. Thus, scabies also should be considered whenever there is intense itching and/or scratching, even without an obvious rash, bite, or burrow. Ulcers are not frequently formed.
  • Scabies frequently occur in the crevasses of the body such as between the fingers and toes, the buttocks, the elbows, the waist area, the genital area, and under the breasts in women. The face, neck, head, scalp, palms, soles of the feet, and lips are usually not affected, except in infants or very young children.
  • Risk factors such as immune suppression or old age may predispose patients to more extensive disease. In crusted (Norwegian) scabies, the body of the infested person is covered with a thick, dry, and scaly rash. The rash of crusted scabies may or may not itch, but it contains thousands to millions of mites. Crusted scabies is the most contagious form of scabies and the hardest to treat.
  • Many other skin rashes may look like scabies, including allergic drug reactions, contact dermatitis, and viral rashes such as shingles.

When Should Someone Seek Medical Care for Scabies?

You should see a medical professional if you suspect you have scabies because treatment of the condition requires prescription medications. Also, other conditions may cause rashes that itch, and it is important to have the correct diagnosis when considering treatment options. When calling to schedule an appointment, be sure to tell your health care provider's staff that you are concerned that you or your child may have scabies.

If you still have symptoms two weeks after treatment, you should be reevaluated by a physician. Sometimes the itching takes a while to go away. It is also possible to get reinfected.

How Do Health Care Professionals Diagnose Scabies?

Most cases of scabies are diagnosed by describing the symptoms to the health care provider who will examine the skin. There is no blood test for scabies, and delays in diagnosis or misdiagnosis are common in low-prevalence areas.

  • Sometimes, the health care provider will do a skin scraping to make or confirm the diagnosis. This is performed by placing a drop of oil or saline on top of an affected area of skin. The area is scraped lightly and the scraping is placed on a slide to examine under a microscope. The doctor will look for the mite or its eggs or feces.
  • The health care provider may perform a felt-tip-marker test by drawing a washable felt-tip marker across the rash and then wiping it off with alcohol. This may help to identify a burrow because the ink penetrates deep into the skin.
  • Often, there are very few mites that can be hard to find. Therefore, even if the scrapings are negative, the doctor may still recommend treatment if he or she is very suspicious that scabies is present.

Other conditions are sometimes confused with scabies. The scabies mite has no relation to body lice, although the symptoms may be similar. Scabies is sometimes confused with bedbug bites, but in contrast to scabies, bedbugs are visible to the naked eye and can live for long periods of time without feeding. Chiggers are a type of mite that can feed off human blood, but unlike scabies, they are acquired through contact with vegetation and feed for only a few days. Less commonly, the rashes of other skin problems such as ringworm, shingles, eczema, allergic reactions (hives), jock itch, or impetigo may be confused with that of scabies.

Are There Any Home Remedies for Scabies?

Although there is no good evidence that scabies can be cured without prescription medication from a doctor, there are certain things you can do at home to keep from re-infesting yourself or your family.

  • Wash all clothing, towels, and bed linens that you have used in the last three days. Use hot water. You should use the dryer at high heat rather than air drying. Since the mites can survive on nonliving objects for several days, place the objects that are not machine washable (such as coats and stuffed toys) into a bag and store for a week. Dry-cleaning will also kill the mites.
  • Cut your nails, and clean under them thoroughly to remove any mites or eggs that may be present.
  • Thoroughly vacuum carpets, furniture, bedding, and car interiors, and throw the vacuum-cleaner bag away when finished.
  • Try to avoid scratching. Keep any open sores clean. Itching may be treated with antihistamine medications such as diphenhydramine (Benadryl), hydroxyzine (Atarax), cetirizine (Zyrtec), and promethazine (Phenergan). Topical measures to reduce itching such as cool baths or calamine lotion should not be given while the prescription cream is being used because it will wash the cream off or prevent it from getting into the skin.
  • Shampoo your hair regularly.

Home remedies such as neem or tea tree oil, hydrogen peroxide, Borax, bleach, olive oil and lemon, Lysol, alcohol (rubbing alcohol), apple cider vinegar, and clove oil are largely untested and are not recommended as a substitute for prescription medication according to the CDC. The CDC states that no over-the-counter products have been tested or approved to treat scabies.

What Are Scabies Treatment Options?

The first question affected people ask is how to get rid of scabies. Prescription medications (see below) are available, which kill the scabies mite and thus are known as scabicides.

  • Household members and sexual partners should be treated at the same time regardless of whether or not they have symptoms. Anyone who has had skin-to-skin contact with the patient in the past month should be treated. If a child with scabies attends day care or the affected person is institutionalized (such as in a nursing home or prison), then staff and others in close contact with the person should be treated. It is best to treat everyone simultaneously to minimize the risk that untreated people will re-infest treated people.
  • Occasionally, the scratched skin may become infected, and sores may contain pus or become red and warm. This is a separate condition from scabies and is usually a bacterial infection that develops due to scratching or irritation of the infested skin. If this occurs, it may be treated with an oral antibiotic or an antibiotic ointment applied to the area.
  • The itching and rash may last for up to two weeks after treatment. If the symptoms last longer, it is possible that the person has been re-infested or that the cream was not used appropriately. In some cases, the treatment is repeated after two weeks if symptoms have not gone away.

What Medications Treat Scabies?

Follow all instructions from your doctor when using scabies medications. A package insert will provide added information.

  • Do not apply topical agents to eyes, face, or mucous membranes.
  • Discuss treatment with your doctor if you are pregnant, breastfeeding, or are treating your newborn or a toddler.
  • Common prescription agents for scabies
    • Permethrin 5% cream (Elimite) is the treatment of choice for scabies. Permethrin 5% cream is applied to clean, dry skin. For best results, clip and clean all fingernails and toenails. Permethrin is usually left on the skin for 10-14 hours and then washed off in the shower. It is best to apply permethrin at bedtime and then wash it off in the morning.
  • Less common prescription agents
    • Lindane 1% cream or lotion is an older medication that is rarely used because it is potentially toxic to the nervous system (leading to symptoms such as dizziness or seizures). Some scabies have become resistant to Lindane.
    • Ivermectin pill(s) (Stromectol) is an oral medication that is active against several parasites. It is not FDA-approved for use in scabies but has been used in cases with very heavy infestations. Ivermectin is not used in small children or in women who are pregnant or breastfeeding.
    • Malathion 0.5% lotion (Ovide) is usually used for head lice and is not approved by the U.S. FDA for the treatment of scabies. It is irritating to the skin. It must be used only as directed and should be kept out of the reach of children because ingestion may cause organophosphate poisoning.
    • Benzyl benzoate lotion is an older treatment for scabies. It can be irritating to the skin, especially in people who have eczema.
    • Crotamiton lotion or cream (Eurax) is approved for use in adults with scabies. Treatment failures with this drug are more common than with permethrin.
    • Sulfur-based lotions, creams, or soaps have been used but are less effective than other options. They should not be used in people who are allergic to sulfa.

What Types of Physicians Treat Scabies?

Most primary-care providers (who may be family medicine or internal medicine specialists) and pediatricians treat scabies. Dermatologists and pediatric dermatologists may be consulted to treat some patients with complications (for example, Norwegian scabies).

What Follow-up Is Needed for a Scabies Infestation?

Itching can last for two weeks or more after successful treatment and does not necessarily indicate that the treatment failed. Repeat examination by a doctor in two weeks is recommended if there is persistent itching after treatment.

Is It Possible to Prevent Scabies?

It is difficult to prevent scabies. If a person is known to have scabies, they should not have close skin-to-skin contact with others until they have been treated. If one member of a household has scabies, all other household members, sexual partners, and close contacts should be treated simultaneously. Clothing, towels, and bedding from an affected person should be washed in hot water and dried in a dryer. If an article cannot be washed this way, it can be stored away from human contact for at least three days to eliminate mites because the mites will not survive longer than three days without contacting human skin.

In the hospital, staff should use gloves and gowns when treating patients who have a suspicious rash and itching.

What Is the Prognosis of Scabies?

Once properly diagnosed, treatment is generally very effective at curing scabies and restoring normal skin health. Extensive scratching can cause abrasions on the skin, which may become secondarily infected with bacteria. Secondary infections are a significant problem in developing countries and the tropics.

Scabies Pictures

Picture of small pimple-like lesions in the finger web caused by scabies
Picture of small pimple-like lesions in the finger web caused by scabies; SOURCE: CDC

Picture of scabies mite seen under a high-power microscope lens
Picture of scabies mite seen under a high-power microscope lens; SOURCE: CDC/Joe Miller/Reed & Carnrick Pharmaceuticals

Picture of scabies rash on the hand
Picture of scabies rash on the hand; SOURCE: CDC/Reed and Carnrich Pharmaceuticals

Picture of scabies rash in the groin
Picture of scabies rash in the groin; SOURCE: CDC/Susan Lindsley

Reviewed on 8/30/2017
Sources: References

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