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Scabies

Definition

Scabies is an easily spread skin disease caused by a very small species of mite.

Alternative Names

Sarcoptes scabiei

Causes, incidence, and risk factors

Scabies is found worldwide among people of all groups and ages. It is spread by direct contact with infected people, and less often by sharing clothing or bedding. Sometimes whole families are affected.

Outbreaks of scabies are more common in nursing homes, nursing facilities, and child care centers.

The mites that cause scabies burrow into the skin and deposit their eggs, forming a burrow that looks like a pencil mark. Eggs mature in 21 days. The itchy rash is an allergic response to the mite.

Scabies is spread by skin-to-skin contact with another person who has scabies.

Pets and animals cannot spread human scabies. It is also not very likely for scabies to be spread by:

• A swimming pool
• Contact with the towels, bedding, and clothing of someone who has scabies, unless the person has what is called "crusted scabies"

Symptoms

• Itching, especially at night
• Rashes, especially between the fingers
• Sores (abrasions) on the skin from scratching and digging
• Thin, pencil-mark lines on the skin

Mites may be more widespread on a baby's skin, causing pimples over the trunk, or small blisters over the palms and soles.

• In young children, the head, neck, shoulders, palms, and soles are involved.
• In older children and adults, the hands, wrists, genitals, and abdomen are involved.

Signs and tests

Examination of the skin shows signs of scabies. Tests include an examination under the microscope of skin scrapings taken from a burrow to look for the mites. A skin biopsy can also be done.

Treatment

Prescription medicated creams are commonly used to treat scabies infections. The most commonly used cream is permethrin 5%. Other creams include benzyl benzoate, sulfur in petrolatum, and crotamiton. Lindane is rarely used because of its side effects.

Creams are applied all over the body. The whole family or sexual partners of infected people should be treated, even if they do not have symptoms. Creams are applied as a one-time treatment or they may be repeated in 1 week.

Wash underwear, towels, and sleepwear in hot water. Vacuum the carpets and upholstered furniture.

For difficult cases, some health care providers may also prescribe medication taken by mouth to kill the scabies mites. Ivermectin is a pill that may be used.

Itching may continue for 2 weeks or more after treatment begins, but it will disappear if you follow your health care provider's treatment plan. You can reduce itching with cool soaks and calamine lotion. Your doctor may also recommend an oral antihistamine.

Support Groups

Expectations (prognosis)

Most cases of scabies can be cured without any long-term problems. A severe case with a lot of scaling or crusting may be a sign that the person has a disease such as HIV.

Complications

Intense scratching can cause a secondary skin infection, such as impetigo.

Calling your health care provider

Call your health care provider if:

• You have symptoms of scabies
• A person you have been in close contact with has been diagnosed with scabies

Prevention

Avoid contact with infected persons.

References

Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier;2009:pp 582-589.

Diaz JH. Scabies. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Churchill Livingstone Elsevier;2009:chap 294.