Scabies
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Scabies

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Definition

Scabies is an infestation of the skin most commonly caused by a tiny mite called the Sarcoptes scabiei .

Scabies

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Causes

Scabies infestation results when the female mite burrows into the skin and lays its eggs. The scabies mite does not suck blood, and it does not transmit any disease other than scabies between people.

Scabies is highly contagious. Most often, it is passed from person to person through:

  • Close and generally prolonged physical contact
  • Sexual contact

Scabies can also spread from person to person by sharing:

  • Clothing
  • Towels
  • Bedding

Scabies can occasionally also be acquired from certain mammals, most commonly dogs with “sarcoptic mange.” Scabies acquired from dogs differs somewhat from human scabies and rarely, if ever, passes from person to person.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Your risk of scabies increases with:

  • Age: less than 15 years, or older than 65 years
  • Sexual contact with new or multiple partners
  • Close, physical contact with a person who has scabies
  • Living in close quarters with others (such as in a nursing home or military barracks)
  • A weakened immune system
  • Close contact with animal scabies

Symptoms

Symptoms of scabies include:

  • Intense itching, usually worse at night
  • Small red bumps, pimples, or lines on the skin

In more severe cases, the infested area may:

  • Appear crusty
  • Become infected and discharge pus

Except in infants or those with abnormalities of the immune system, scabies rarely affects the face or head. While any other body area, or even the whole body, may be involved, areas most often affected include:

  • Hands, especially between the fingers
  • Wrists and elbows
  • Feet
  • Genitals and pubic area (especially in men)
  • Buttocks
  • Around the nipples (especially in women)
  • Waistline
  • Bellybutton and lower abdomen
  • Areas where clothing is tight
  • Under rings, watches, or jewelry

Diagnosis

The doctor will ask about symptoms and medical history, and perform a physical exam. While scabies can often be diagnosed based on symptoms and the physical exam, the doctor may scrape some skin off an infested area and view the contents under a microscope to confirm the diagnosis.

Treatment

It is essential to remove scabies from the living environment to avoid re-infestation after treatment. All bedding and clothing must be thoroughly laundered. Other members of the household or institution ought to be treated unless there is a compelling reason not to.

Scabies is usually treated by applying permethrin cream 5% to the skin from the neck down and left on for 8-12 hours. Because excessive use of this medication can be harmful, carefully read and follow the directions. Do not repeat treatments unless told to do so by a physician.

It may take several weeks for itching to disappear following successful treatment. If new, itchy bumps continue to appear in the days following your treatment, be sure to alert your doctor. An antihistamine or corticosteroid cream may help relieve itching temporarily.

In severe cases that are poorly responsive to other treatments, an oral medication, called ivermectin, is sometimes prescribed as a single dose. Alternative topical creams include crotamiton 10% and lindane 1%.

Lindane, a second line treatment, should only be prescribed to patients who are unable to take other medications or who have not responded to them. According to the Food and Drug Administration’s warning, lindane can rarely cause serious side effects, including seizure and death. Those especially susceptible are infants, the elderly, children and adults weighing under 110 lbs, and individuals with other skin conditions. Lindane can be toxic and should not be overused. Patients are given small amounts (1-2 oz) of the shampoo or lotion and instructed to apply a very thin layer and not to reapply. For more information, visit the Center for Drug Evaluation and Research website .

Prevention

To reduce your risk of getting scabies:

  • Avoid close physical contact or sharing clothing, towels, or bedding with anyone who has either scabies or an undiagnosed itchy rash, especially a rash that has been present for over a week.
To prevent the spread of scabies from one person to another:

  • Make sure those who share living quarters with the affected individual are considered for treatment.
  • Wash or dry clean all clothing, bedding, and towels that may have become infested. Mites may live for at least 2-5 days after they leave a human body and are probably infectious during some or all of that time.
  • Consider vacuuming the entire living area and throwing away the vacuum bag afterward. There is, however, no evidence that vacuuming or other house cleaning activities are needed to reduce the spread of scabies. Spread by any means other than direct skin-to-skin contact is very rare.

RESOURCES:

The American Academy of Dermatology
http://www.aad.org

MedlinePlus
http://medlineplus.gov

CANADIAN RESOURCES

Communicable Disease Control (CDC) Network
Province of Manitoba
http://www.gov.mb.ca/health/publichealth/cdc/index.html

Health Canada
http://www.hc-sc.gc.ca/

References:

AHFS Drug Information website. Available at: http://www.ashp.org/ahfs/index.cfm .

American Academy of Dermatology website. Available at: http://www.aad.org .

Lindane shampoo and lindane lotion. Center for Drug Evaluation and Research. US Food and Drug Administration website. Available at: http://www.fda.gov/cder/drug/infopage/lindane/default.htm . Accessed March 12, 2007.

Medical Diagnosis and Treatment . 44th ed. 2005.

Medication guide lindane (LIHN-dane) lotion USP, 1%. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.fda.gov/cder/drug/infopage/lindane/lindaneLotionGuide.htm . Accessed March 12, 2007.

Medication guide lindane (LIHN-dane) shampoo USP, 1%. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.fda.gov/cder/drug/infopage/lindane/lindaneShampooGuide.htm . Accessed March 12, 2007.

The Merck Manual of Medical Information—Home Edition . Simon and Schuster, Inc; 2000.

National Institute of Allergy and Infectious Diseases website. Available at: http://www3.niaid.nih.gov/ .

Revised lindane lotion label. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.fda.gov/cder/foi/label/2003/006309lotionlbl.pdf . Accessed March 12, 2007.

Revised lindane shampoo label. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.fda.gov/cder/foi/label/2003/006309shampoolbl.pdf . Accessed March 12, 2007.



Last reviewed October 2007 by Ross Zeltser, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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