Scabies

Human itch mite: This female mite, shown magnified 100 times, is full of eggs. She will burrow into human skin to lay her eggs.

Scabies: Overview

A mite causes this common skin condition. Called the human itch mite, this eight-legged bug is so small that you cannot see it on the skin. People get scabies when the mite burrows into the top layer of skin to live and feed. When the skin reacts to the mite, an extremely itchy rash develops. 

This mite can travel from the infected person to another person. Most people get scabies from direct, skin-to-skin contact. Less often, people pick up mites from infested items such as bedding, clothes, and furniture. The mite can survive for about 48 to 72 hours without human contact. Worldwide, there are millions of cases of scabies each year.

Anyone can get scabies. It strikes people of all ages, races, and income levels. People who are very clean and neat can get scabies. It tends to spread easily in nursing homes and extended-care facilities. The good news is that a dermatologist can successfully diagnose and treat scabies. With today’s treatments, scabies need only cause short-term distress.

Scabies: While spending time in a rehabilitation facility, this 75-year-old man developed scabies.

Scabies: Signs and symptoms

After the mite burrows into the skin, it takes time to develop signs and symptoms. If a person has had scabies before, the itching usually begins within 1 to 4 days. When a person has not had scabies, the body needs time to develop a reaction to the mite. It can take 2 to 6 weeks to develop symptoms.

Signs and symptoms of scabies include:

• Itching, mainly at night: Itching is the most common symptom. The itch can be so intense that it keeps a person awake at night.
• Rash: Many people get the scabies rash. This rash causes little bumps that often form a line. The bumps can look like hives, tiny bites, knots under the skin, or pimples. Some people develop scaly patches that look like eczema.
• Sores: Scratching the itchy rash can cause sores. An infection can develop in the sores.
• Thick crusts on the skin: Crusts form when a person develops a severe type of scabies called crusted scabies. Another name for crusted scabies is Norwegian scabies. These crusts house 100s to 1,000s of mites and the mites’ eggs. With so many mites burrowing in the skin, the rash and itch become severe.

The severe itch can lead to constant scratching. With non-stop scratching, an infection can develop. Non-stop scratching can even lead to sepsis, a sometimes life-threatening condition that develops when the infection enters the blood.

Scabies can develop anywhere on the skin. The mites, however, prefer to burrow in certain parts of the body. The most common places to have itching and a rash are:

• Hands: Mites like to burrow in the skin between the fingers and around the nails.
• Arms: Mites like the elbows and wrists.
• Skin usually covered by clothing or jewelry: The buttocks, belt line, penis, and skin around the nipples are likely places for mites to burrow. Mites also like to burrow in skin covered by a bracelet, watchband, or ring.

Scabies rash: Small, pus-filled bumps on the sole are often a sign of scabies in infants and young children.

Scabies in children

Some children develop widespread scabies. The scabies rash can cover most of the body. Even a child’s palms, soles, and scalp can be infested with mites. In babies, the rash often appears on the palms and soles. Babies who have scabies are very irritable and often do not want to eat or sleep. Children, too, are often very irritable. The itch can keep them awake at night.

Crusted scabies

Also called Norwegian scabies, crusted scabies is a severe form of scabies. People who have crusted scabies have 100s or even 1,000s of mites in their skin. By comparison, most people who get scabies have 15 to 20 mites on their skin.

Crusted scabies develops in people who have a weak immune system due to a medical condition, the elderly, and people who are living in institutions. Crusted scabies develops when the person’s body cannot develop any resistance to the mites. Without resistance, the mites quickly multiply.

Crusted scabies: Crusts, such as the one on this man’s arm and chest, form when people get crusted scabies, also called Norwegian scabies.

A common sign of crusted scabies is widespread crusts on the skin. These crusts tend to be thick, crumble easily when touched, and look grayish in color. Sometimes the crusts appear on 1 or a few areas of the body such as the scalp, back, or feet.

Images used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.

References:
Chosidow O. Clinical practices. Scabies. N Engl J Med 2006; 354: 1718-27.
Czelusta A, Yen-Moore A, Van der Straten M et al. An overview of sexually transmitted diseases. Part III. Sexually transmitted diseases in HIV-infected patients. J Am Acad Dermatol 2000; 43: 409-32; quiz 33-6.
Habif, Campbell, Chapman, et al. In: Dermatology DDxDeck. 2006. China. Mosby Elsevier. Card #92: Scabies.
Steen CJ, Carbonaro PA, Schwartz RA. Arthropods in dermatology. J Am Acad Dermatol 2004; 50: 819-42, quiz 42-4.

Scabies: Who gets and causes

Who gets scabies?

Anyone can get scabies. Because skin-to-skin contact is the most common way to get scabies, the following people are especially susceptible:

• Children.
• Mothers of young children.
• Sexually active young adults.
• Residents of nursing homes, assisted-living residences, and extended-care facilities.

Having a weakened immune system also increases the risk of getting scabies. The elderly and people who have a weak immune system due to disease such as HIV/AIDS, lymphoma, or leukemia have an increased risk. People who received an organ transplant also have a higher risk.

Crusted scabies is especially contagious. A crust filled with mites can fall off. This shed crust can provide food and protection for the mites, allowing them to live for as long as 1 week without human contact.

Scabies among people in nursing homes and extended-care facilities has become a common problem in the United States. The residents often need help with daily tasks, so there is frequent skin-to-skin contact. Scabies can spread to nursing staff. The staff can then spread scabies to other residents. This can happen quickly.

Scabies can spread when people do not have any signs or symptoms. A person who has never had scabies often does not have any signs or symptoms for 2 to 6 weeks.

What causes scabies?

The human itch mite causes scabies. People get scabies when the mite burrows into the skin. You can get the mite on your skin through:

• Direct skin-to-skin contact. 
• Contact with an infested object such as a towel, bedding, or upholstered furniture.

You cannot get scabies from an animal that has mites. Only humans get this type of scabies.

Most people will not get scabies from a handshake or hug. The skin-to-skin contact must be longer for a mite to crawl from one person to another. Adults often get scabies through sexual contact. 

Images used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.

References:
Czelusta A, Yen-Moore A, Van der Straten M et al. An overview of sexually transmitted diseases. Part III.
Sexually transmitted diseases in HIV-infected patients. J Am Acad Dermatol 2000; 43: 409-32; quiz 33-6.
Habif, Campbell, Chapman, et al. In: Dermatology DDxDeck. 2006. China. Mosby Elsevier. Card #92: Scabies.
Jacobson CC, Abel EA. Parasitic infestations. J Am Acad Dermatol 2007; 56: 1026-43.

Scabies: Diagnosis and treatment

How do dermatologists diagnose scabies?

A dermatologist can often diagnose scabies by visually examining a patient’s skin from head to toe.

To make sure that a patient has scabies, a dermatologist may scrape off a tiny bit of skin. This is painless. Your dermatologist will put the skin on a glass slide and look at the slide under a microscope. If your dermatologist sees scabies mites or their eggs, it is certain that you have scabies.

How do dermatologists treat scabies?

To get rid of scabies, treatment is essential. Medicine that treats scabies is only available with a doctor’s prescription.

Who needs treatment?

The person diagnosed with scabies and everyone who has had close contact with that person need treatment. Even people who do not have any signs or symptoms must be treated. This is the only way to prevent new outbreaks of scabies weeks later. People who should be treated include:

• Everyone who lives with the person.
• Recent sexual partners.

Most people can be cured with a medicine that they apply to their skin. These medicines are often applied to all skin from the neck down. Infants and young children often need treatment for their scalp and face, too. A dermatologist will provide specific instructions to follow.

Most medicine is applied at bedtime. The medicine is then washed off when the patient wakes up. You may need to repeat this process one week later.

It is important to follow your dermatologist’s instructions. Treating the skin more often than instructed can worsen the rash and itching.

Medicines that may be prescribed include:

• 5% permethrin cream: This is the most common treatment for scabies. It is safe for children as young as 1 month old and women who are pregnant. 
• 25% benzyl benzoate lotion.
• 10% sulfur ointment. 
• 10% crotamiton cream.
• 1% lindane lotion.

Treatment for widespread scabies: Scabies that covers much of the body and crusted scabies often require stronger medicine. A patient with this type of scabies may receive a prescription for ivermectin. This medicine can be prescribed to children and patients who are HIV-positive. Many patients need only to take 1 dose. Some patients need to take 2 or 3 doses to cure scabies. The pills are usually taken one week apart.

When scabies infects many people at a nursing home, extended-care facility, and other institution, ivermectin may be prescribed to everyone who has a risk of catching scabies.

Other signs and symptoms: Some patients need other treatment, too. Your dermatologist may prescribe:

• Antihistamine: To control the itch and help you sleep.
• Pramoxine lotion: To control the itch.
• Antibiotic: To wipe out an infection.
• Steroid cream: To ease the redness, swelling, and itch.

Outcome

Treatment can get rid of the mites, eliminate symptoms such as itch, and treat an infection that has developed. For the first few days to a week, the rash and itch can worsen during treatment. Within 4 weeks, your skin should heal.

If your skin has not healed within 4 weeks, you may still have mites. Some people need to treat 2 or 3 times to get rid of the mites. Be sure to see your dermatologist for treatment. You should never use a scabicide used to treat crops or livestock.

People who develop crusted scabies, also known as Norwegian scabies, often need repeat treatments to get rid of the mites.

To get rid of the mites and prevent getting scabies again, you have to do more than treat the skin or take a pill. You will need to wash clothes, bedding, and towels to get rid of mites that may have fallen off your skin. You also should vacuum your entire home.

References:
Chosidow O. Clinical practices. Scabies. N Engl J Med 2006; 354: 1718-27.
Czelusta A, Yen-Moore A, Van der Straten M et al. An overview of sexually transmitted diseases. Part III. Sexually transmitted diseases in HIV-infected patients. J Am Acad Dermatol 2000; 43: 409-32; quiz 33-6.
Elston DM. Controversies concerning the treatment of lice and scabies. J Am Acad Dermatol 2002; 46: 794-6.
Habif, Campbell, Chapman, et al. In: Dermatology DDxDeck. 2006. China. Mosby Elsevier. Card #92: Scabies.
Jacobson CC, Abel EA. Parasitic infestations. J Am Acad Dermatol 2007; 56: 1026-43.
Steen CJ, Carbonaro PA, Schwartz RA. Arthropods in dermatology. J Am Acad Dermatol 2004; 50: 819-42, quiz 42-4.

Washing clothes, bedding, and towels is necessary to get rid of the mites that cause scabies.

Scabies: Tips for managing

The mite that causes scabies is hardy. These tips can help you get rid of the mites. 

1. If you think you have scabies, don’t be embarrassed to see a dermatologist. Some people do not seek medical help because they feel this reflects poorly on them. This is not true. People who are very clean and neat can get scabies. People of all ages, races, and income levels get scabies.
2. Everyone with whom you had close contact needs treatment. Scabies is very contagious. If you get treatment and people with whom you live or have close contact do not get treatment, you can get the mites again. People do not have to have signs and symptoms of scabies to have mites on their skin. Someone who has never had scabies may not have any symptoms for 2 to 6 weeks. 
3. If your dermatologist prescribes a medicine that you apply to your skin, be sure to take a bath or shower before you apply the medicine. You should then massage the medicine onto clean, dry skin. The medicine must remain on the skin for 8 to 14 hours. You will then wash off the medicine. For this reason, most people apply the medicine at bedtime and wash it off in the morning. 
4. Apply the medicine from your neck to your toes. This includes all skin between your neck and toes — the skin around your nails, the crease between your buttocks, and the skin between your toes. Infants, children, and the elderly often need to treat their scalp, temples, and forehead. You should never apply medicine to the nose, lips, eyelids, nor around the eyes or mouth.
5. If you wash your hands after applying the medicine, be sure to reapply the medicine to your hands. Mites like to burrow in the hands, so it is important to treat the hands. Be sure to apply the medicine to the skin between your fingers.
6. The day you start treatment, wash your clothes, bedding, towels, and washcloths. Mites can survive for a few days without human skin. If a mite survives, you can get scabies again. To prevent this, you must wash clothes, sheets, comforters, blankets, towels, and other items. Be sure to follow these instructions when washing: 
   
   • Wash all items in a washing machine, using the hottest water possible.
   • After washing, dry everything in a dryer, using the hot setting.
   • If you cannot wash something in a washing machine and then dry it in a dryer, take it to a dry cleaner or seal it in plastic bag for at least 1 week.
   • Items that have not touched your skin for more than 1 week generally do not need washing. If you are not sure whether you wore clothing or used an item within the past week, be sure to wash and dry it.
7. Vacuum your entire home on the day you start treatment. Vacuum carpeting, area rugs, and all upholstered furniture.
8. Do not treat your pets. The human itch mite cannot survive on animals. Pets do not need treatment.

References:
Habif, Campbell, Chapman, et al. In: Dermatology DDxDeck. 2006. China. Mosby Elsevier. Card #92: Scabies.
Jacobson CC, Abel EA. Parasitic infestations. J Am Acad Dermatol 2007; 56: 1026-43

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