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Blake Medical Center
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Crab Lice

Definition

Crabs, or pubic lice, are tiny, barely visible parasites. They are usually found in the pubic hair but can also be found in other body areas with short hair. This may include eyelashes, eyebrows, armpit hair, and mustache hair.

Pubic lice are commonly called crabs because they look like tiny crabs.

Pubic Louse
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Causes

Crab lice are parasites. Parasites are insects that need to live off of another animal. Crab lice are spread by personal contact, usually during sexual activity. Less often, crab lice may also spread by sharing personal items. This can include sharing bedding, towels, and clothing.

Risk Factors

Factors that increase your risk for crab lice include:

  • Sexual contact with someone who has crab lice
  • Contact with contaminated items, such as:
    • Bedding
    • Towels
    • Clothing

Symptoms

Symptoms include:

  • Itchiness that can range from mild to severe
  • Tiny blue bumps on the skin
  • Lice or eggs visible on hair

Diagnosis

You will be asked about your symptoms and medical history. A physical exam will be done. Your doctor will be able to diagnose crab lice by the appearance of lice and lice eggs in your pubic area.

Your doctor may also check you for other sexually transmitted infections.

Treatment

Over-the-counter shampoo or cream rinse containing permethrin or pyrethrins are used to treat pubic lice.

Some lice may be resistant to this treatment. For resistant cases, your doctor may advise:

  • Malathion—a prescription topical medication approved only for patients older than 6 years
  • Lindane—a prescription topical medication
    • Note: Lindane 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. It should also not be used in pregnant or lactating women or in people who have uncontrolled seizures. Lindane is a toxin 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.
  • Ivermectin—a medication given by mouth. It cannot be used in pregnant or lactating women

Prevention

To reduce the chance of getting crabs or spreading crabs:

  • Limit sexual partners.
  • Watch for signs of crabs, such as itching in the genital area.
  • If you or someone in your house has had crabs, thoroughly wash and dry bedding, towels, and clothing.
  • If you have had crabs, inform any sexual partners that they are at risk for crabs. Avoid sexual activity until partners have been treated.

Revision Information

  • American Academy of Dermatology

    http://www.aad.org

  • American College of Obstetrics and Gynecology

    http://www.acog.org

  • HealthLink BC

    http://www.healthlinkbc.ca

  • Health Canada

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

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

  • Lindane shampoo and lindane lotion. US Food and Drug Administration website. Available at: http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm110452.htm. Updated June 18, 2009. Accessed May 28, 2015.

  • Medication guide lindane shampoo. US Food and Drug Administration website. Available at: http://www.accessdata.fda.gov/drugsatfda%5Fdocs/label/2003/006309shampoolbl.pdf. Updated April 2002. Accessed May 28, 2015.

  • Parasites—lice. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/lice/pubic/factsheet.html. Updated September 24, 2013. Accessed May 28, 2015.