Scabies

Definition

Scabies is an infestation of the skin. It is caused by a tiny mite.
Scabies
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Causes

An infestation results when the female mite burrows into the skin and lays its eggs. The scabies mite does not suck blood. 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. It is most common from dogs with sarcoptic mange. Scabies from dogs differs somewhat from human scabies. It rarely passes from person to person.

Risk Factors

Children younger than 15 years of age and adults older than 65 years are at greater risk for this condition. Factors that increase your chance of scabies include:
  • 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 an animal with 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
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
  • Belly button and lower abdomen
  • Areas where clothing is tight
  • Under rings, watches, or jewelry

Diagnosis

You will be asked about your about symptoms and medical history. A physical exam will be done. While scabies can often be diagnosed based on these steps, a skin sample may be taken. The sample is examined 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 washed. Other members of the household or facility should be treated.

Permethrin Cream 5%

Scabies is usually treated by applying permethrin cream 5%. It is applied to the skin from the neck down. The cream is left on for 8-12 hours, usually overnight. Excessive use of this medication can be harmful, especially in infants. Carefully read and follow the directions. It is best not to repeat treatments unless told to do so by a doctor.

Itch Relief

It may take several weeks for itching to disappear following successful treatment. Itching can be temporarily relieved with:
  • Antihistamine
  • Corticosteroid cream
  • Antihistamines and corticosteroids

Alternative Medications

Some severe cases may respond poorly to treatments. In this case, an oral medicine, called ivermectin, is sometimes prescribed. It is given as a single dose that must be repeated after 1 week.Alternative topical creams include crotamiton 10% and lindane 1%.Lindane should only be used when other medications have not been effective. Lindane can be toxic. It should not be overused. Follow the directions as given.

Prevention

To reduce your risk of getting scabies, avoid close physical contact with anyone who has either had scabies or has had an undiagnosed itchy rash. Do not share their:
  • Clothing
  • Towels
  • Bedding
To prevent the spread of scabies from one person to another:
  • If you share living quarters with an infected person and/or have close physical contact, consider treatment even if you do not have symptoms.
  • Wash or dry clean all clothing, bedding, and towels that may have become infested. Set washing or drying temperatures to 140ºF (60ºC) or higher. Mites may live for at least 2-5 days after they leave a human body. They are probably infectious during some or all of that time, especially in room temperatures of 68ºF (20ºC) and above. Some experts suggest that items that cannot easily be cleaned be placed in a plastic bag for at least 3 days.
  • Try to avoid contact for several days with hard-to-clean or non-cleanable items, like upholstered furniture. Talk to your doctor about ways to deal with household items that cannot be cleaned.

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RESOURCES

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

Family Doctor—American Academy of Family Physicians
http://familydoctor.org

CANADIAN RESOURCES

Canadian Dermatology Association
http://www.dermatology.ca

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

References

Centers for Disease Control and Prevention. Sexually Transmitted Diseases Treatment Guidelines, 2010. MMWR 2010;59(No. RR-12):1-110.

Currie BJ, McCarthy, JS. Permethrin and ivermectin for scabies. New Engl J of Med. 2010: 362:717-725.

Hu S, Bigby M. Treating scabies: results from an updated Cochrane review. Arch Dermatol. 2008:144:1638-40.

Leone PA. Scabies and pediculosis pubis: an update of treatment regimens andgeneral review. Clin Infect Dis. 2007 Apr 1;44 Suppl 3:S153-9. Review. Available at: http://cid.oxfordjournals.org/content/44/Supplement%5F3/S153.long.Accessed January 15, 2015.

Lindane shampoo and lindane lotion. Center for Drug Evaluation and Research. US Food and Drug Administration website. Available at: http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm110452.htm. Updated June 18, 2009. Accessed January 15, 2015.

Medication guide lindane lotion USP, 1%. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.fda.gov/downloads/Drugs/DrugSafety/UCM133687.pdf. Updated August 2007. Accessed January 15, 2015.

Medication guide lindane shampoo USP, 1%. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.fda.gov/downloads/Drugs/DrugSafety/UCM133688.pdf. Updated August 2007. Accessed January 15, 2015.

Mumcuoglu KY, Gilead L. Treatment of scabies infestations. Parasite. 2008;15: 248-51.

Revised lindane lotion label. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.accessdata.fda.gov/drugsatfda%5Fdocs/label/2003/006309lotionlbl.pdf. Accessed January 15, 2015.

Revised lindane shampoo label. Center for Drug Evaluation and Research. Food and Drug Administration website. Available at: http://www.accessdata.fda.gov/drugsatfda%5Fdocs/label/2003/006309shampoolbl.pdf. Accessed January 15, 2015.

Strong M, Johnstone PW. Interventions for treating scabies. Cochrane Database Syst Rev. 2007 Jul 18;(3):CD000320. Review.

Wolf R, Davidovici B. Treatment of scabies and pediculosis: facts andcontroversies. Clin Dermatol. 2010 Sep-Oct;28(5):511-518.

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