Scabies is a parasitic skin infestation caused by mites.
Scabies usually spreads from person to person through physical contact.
People with scabies have severe itching, even though there are typically few mites on the body.
Doctors diagnose scabies by examining the itchy areas and sometimes by looking at skin scrapings under a microscope.
Treatments of scabies include permethrin or spinosad applied to the skin and ivermectin taken by mouth.Treatments of scabies include permethrin or spinosad applied to the skin and ivermectin taken by mouth.
Parasites are organisms that live on or inside another organism (the host) and depend on the host for nutrition to live. The mites that cause scabies are parasites because they live by feeding on a person's blood.
Scabies is caused by the mite Sarcoptes scabiei. Infestations occur worldwide. The female mite bites and tunnels into the topmost layer of the skin and deposits her eggs in burrows. Young mites (larvae) then hatch in a few days. The infestation causes intense itching, probably due to an allergic reaction to the mites. (See also Mite Bites.)
The infestation spreads easily from person to person through physical contact, often spreading through an entire household. Human mites can live on fomites, which are physical objects such as towels, bedding, and clothing, from which they can infect people. However, once away from the human body, mites do not live very long. Animal mites may be spread to humans and cause itching, but they do not live very long or require treatment. Mites that cause scabies are usually destroyed by normal laundering (machine washing in hot water followed by drying in a hot dryer or ironing) or dry cleaning. The main risk factor is crowded conditions (as in schools, shelters, barracks, and some households). Scabies is not related to poor hygiene. The burden of scabies is particularly high in Latin America and some island countries in the Pacific region (such as Fiji).
Symptoms of Scabies Infestation
Symptoms of scabies first begin to appear around 4 to 6 weeks after initial exposure. The hallmark of scabies is intense itching, which is usually worse at night. The burrows of the mites are often visible as very thin lines up to a ½ inch (about 1 centimeter) long, sometimes with a tiny reddish and very itchy bump—the mite—at one end. Often, this may be followed by the formation of a fluid filled blister. Sometimes, scratching of the itchy blisters can cause them to break open, which can result in a bacterial infection of the skin (so-called secondary infection). Sometimes, only tiny bumps are seen, many of which are scratched open because of the itching.
The bumps can be anywhere on the body, including the breasts and penis. The bumps do not appear on the face in adults. The bumps first appear on the webs between the fingers, wrists, inner elbows, underarms, along the belt line, or buttocks. Over time, the burrows may become difficult to see because they are obscured by inflammation induced by scratching. People in warm climates develop small red bumps with few burrows.
In people with dark skin, scabies can cause solid raised areas. In infants, the palms, soles, face, and scalp may be affected, especially behind the ears. In older adults, scabies can cause intense itching but very mild skin symptoms, which makes it a challenge for doctors to diagnose.
This photo shows red scabies bumps in the webbing between fingers.
This photo shows red scabies bumps in the webbing between fingers.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
The child in this photo has scratches and tiny reddish bumps clustered on the forearm and palm and in the creases of the wrist. These findings are typical of scabies. Burrows are ½-inch-long (about 1 centimeter-long) crusted bumps in the creases of the wrist and elsewhere.
The child in this photo has scratches and tiny reddish bumps clustered on the forearm and palm and in the creases of th
Photo courtesy of Karen McKoy, MD.
This photo shows raised areas of scabies on the soles of an infant.
This photo shows raised areas of scabies on the soles of an infant.
© Springer Science+Business Media
This photo shows red scabies bumps in the webbing between fingers.
This photo shows red scabies bumps in the webbing between fingers.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
The child in this photo has scratches and tiny reddish bumps clustered on the forearm and palm and in the creases of the wrist. These findings are typical of scabies. Burrows are ½-inch-long (about 1 centimeter-long) crusted bumps in the creases of the wrist and elsewhere.
The child in this photo has scratches and tiny reddish bumps clustered on the forearm and palm and in the creases of th
Photo courtesy of Karen McKoy, MD.
This photo shows raised areas of scabies on the soles of an infant.
This photo shows raised areas of scabies on the soles of an infant.
© Springer Science+Business Media
People who may develop a severe infestation (called crusted scabies or Norwegian scabies) include:
Those with a weakened immune system (caused by human immunodeficiency virus [HIV] infection, blood cancer, or chronic use of steroids [sometimes also called glucocorticoids or corticosteroids] or other medications that suppress the immune system)
Those with severe physical disabilities or intellectual disability
Those with Aboriginal Australian ethnicity
Children are affected more often than adolescents and adults. Severe infestations cause large areas of thickened, crusted skin (particularly on the palms and soles in adults and on the scalp in children) that may resemble eczema but do not itch.
This photo shows crusted scabies in a person who has human immunodeficiency virus (HIV) infection.
Scabies incognito is a different form of scabies that develops in people who use topical steroids for extended periods of time. It is sometimes hard to recognize because it looks different from the usual forms of scabies, and the mites may be very difficult to find.
Diagnosis of Scabies Infestation
A doctor's evaluation
Burrow scrapings
Usually, itching and the appearance of bumps and burrows are all that are needed to make a diagnosis of scabies. Sometimes doctors use a lens to magnify the skin and make the burrows visible. However, doctors often confirm the presence of mites, eggs, or mite feces by taking a scraping from the bumps or burrows and looking at it under a microscope.
Treatment of Scabies Infestation
Permethrin or other scabicide creamPermethrin or other scabicide cream
Sometimes ivermectinSometimes ivermectin
Sometimes medications to control itching
For older children and adults, scabies can be cured by applying a cream containing permethrin or other scabicide (medication that kills the scabies mite) to the entire body from the neck down and washing it off after 8 to 14 hours. This treatment is repeated a week later.scabies can be cured by applying a cream containing permethrin or other scabicide (medication that kills the scabies mite) to the entire body from the neck down and washing it off after 8 to 14 hours. This treatment is repeated a week later.
For infants and young children, permethrin is applied to the head and neck, avoiding the skin around the eyes and mouth, and over the entire body. The skinfolds, fingernails, toenails, and the navel should be thoroughly treated. Mittens can be put on infants to keep them from putting permethrin is applied to the head and neck, avoiding the skin around the eyes and mouth, and over the entire body. The skinfolds, fingernails, toenails, and the navel should be thoroughly treated. Mittens can be put on infants to keep them from puttingpermethrin in their mouth. Additionally for infants, an ointment containing a formulation of sulfur in petrolatum can be applied at night and washed off in the morning. Lindane is no longer recommended because of its toxic side effects.in their mouth. Additionally for infants, an ointment containing a formulation of sulfur in petrolatum can be applied at night and washed off in the morning. Lindane is no longer recommended because of its toxic side effects.
For adults and children 4 years of age and older, spinosad suspension (liquid) is applied to all of the skin from the neck down, including the soles of the feet. In bald people, the lotion should also be applied to the scalp, forehead, hairline, and temples. It should be allowed to dry for 10 minutes before getting dressed and then left on the skin for 6 hours before showering or bathing. This treatment should be repeated in 1 week. Contact with the eyes should be avoided.spinosad suspension (liquid) is applied to all of the skin from the neck down, including the soles of the feet. In bald people, the lotion should also be applied to the scalp, forehead, hairline, and temples. It should be allowed to dry for 10 minutes before getting dressed and then left on the skin for 6 hours before showering or bathing. This treatment should be repeated in 1 week. Contact with the eyes should be avoided.
Ivermectin taken by mouth in 2 doses given a week apart also is effective for people who are not helped by or cannot take medications applied directly to the skin and is especially helpful for severe infestations in people with a weakened immune system.Ivermectin taken by mouth in 2 doses given a week apart also is effective for people who are not helped by or cannot take medications applied directly to the skin and is especially helpful for severe infestations in people with a weakened immune system.
Even after successful treatment that kills the mites, itching and bumps may persist for up to 3 weeks because of a continued allergic reaction to the mite bodies, which remain in the skin for a while. The itching can be treated with antihistamines taken by mouth. Sometimes mild steroid (sometimes also called a glucocorticoid or corticosteroid) cream is used to help with the itch, but only after the mites have been successfully treated. Occasionally, the skin irritation and deep scratches lead to a bacterial infection, which may require antibiotics given by mouth.
Clothing, towels, and bedding used during the preceding few days should be washed in hot water and dried in a hot dryer, dry cleaned, or put in a closed plastic bag for at least 3 days.
Prevention of Scabies Infestation
The main goals of scabies prevention are to stop the spread by avoiding contact with infected people and their belongings, and to kill the mites on people who are infested as well as the mites in their environment. Family members and people who have had close physical contact, such as sexual contact, with a person with scabies should also be treated. Symptoms can sometimes take weeks to appear, but it is important to remember that an infected person is contagious the entire time. Clothes, bedding, and other linens should be washed in hot water (at least 50°C [122°F]) and dried with high heat, or sealed in a plastic bag for up to 1 week. Only items that have been in contact with the infected person in the last 2 to 3 days need to be cleaned.
Mass treatment with oral ivermectin or a topical cream like permethrin has been found to be very effective in controlling outbreaks.Mass treatment with oral ivermectin or a topical cream like permethrin has been found to be very effective in controlling outbreaks.
