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Pubic lice

Pediculosis - pubic lice; Lice - pubic; Crabs; Pediculosis pubis; Phthirus pubis

Pubic lice are tiny wingless insects that infect the pubic hair area and lay eggs there. These lice can also be found in armpit hair, eyebrows, moustache, beard, around the anus, and eyelashes (in children).

Causes

Pubic lice are most commonly spread during sexual activity.

In very rare cases, pubic lice can spread through contact with objects such as toilet seats, sheets, blankets, or bathing suits (that you may try on at a store).

Animals cannot spread lice to humans.

Other types of lice include:

You are at greater risk for pubic lice if you:

  • Have many sexual partners (high incidence in men who have sex with men)
  • Have sexual contact with an infected person
  • Share bedding or clothing with an infected person

Symptoms

Pubic lice cause itching in the area covered by pubic hair. Itching often gets worse at night. The itching may start soon after getting infected with lice, or it may not start for up to 2 to 4 weeks after contact.

Other symptoms can include:

  • Local skin reactions to the bites that causes skin to turn red or bluish-gray
  • Sores in the genital area due to bites and scratching

Exams and Tests

Your health care provider will do an exam to look for:

  • The lice
  • Small gray-white oval eggs (nits) attached to the hair shafts in the outer genital area
  • Scratch marks or signs of a skin infection

Because pubic lice may cause an eye infection in young children, eyelashes should be looked at with a high-powered magnifying glass. Sexual transmission, and potential sexual molestation, should always be considered if pubic lice are found in children.

Adult lice are easy to identify with a special magnifying device called a dermoscope. Pubic lice are often referred to as "the crabs" because of their appearance.

Teenagers and adults with pubic lice may need to be tested for other sexually transmitted infections (STIs).

Treatment

MEDICINES

Pubic lice are often treated with medicines that contain a substance called permethrin. To use this medicine:

  • Thoroughly work the medicine into your pubic hair and surrounding area. Leave it on for at least 5 to 10 minutes, or as directed by your provider.
  • Rinse well.
  • Comb your pubic hair with a fine-toothed comb to remove eggs (nits). Applying vinegar to pubic hair before combing may help loosen the nits.

In case of eyelash infestation, applying soft paraffin three times daily for 1 to 2 weeks may help.

Most people need only one treatment. If a second treatment is needed, it should be done 4 days to 1 week later.

Over-the-counter medicines to treat lice include Rid, Nix, LiceMD, among others. Malathione lotion is another option.

Sexual partners should be treated at the same time.

OTHER CARE

While you are treating pubic lice:

  • Wash and dry all clothing and bedding in hot water.
  • Spray items that cannot be washed with a medicated spray that you can buy at the store. You can also seal items in plastic bags for 10 to 14 days to smother the lice.

Outlook (Prognosis)

The proper treatment, including thorough cleaning, should get rid of the lice.

Scratching can make the skin raw or cause a skin infection.

When to Contact a Medical Professional

Call for an appointment with your provider if:

  • You or your sexual partner has symptoms of pubic lice
  • You try over-the-counter lice treatments and they are not effective
  • Your symptoms continue after treatment

Prevention

Avoid sexual or intimate contact with people you who have pubic lice until they have been treated.

Bathe or shower often and keep your bedding clean. Avoid trying on bathing suits while you are shopping. If you must try on swimwear, be sure to wear your underwear. This may prevent you from getting or spreading pubic lice.

References

Burkhart CN, Burkhart CG, Morrell DS. Infestations. In: Bolognia JL, Schaffer JV, Cerroni L, eds. Dermatology. 4th ed. Philadelphia, PA: Elsevier; 2018:chap 84.

Katsambas A, Dessinioti C. Parasitic diseases of the skin. In: Kellerman RD, Bope ET, eds. Conn's Current Therapy 2018. Philadelphia, PA: Elsevier; 2018:976-982.

Marcdante KJ, Kliegman RM. Cutaneous infestations. In: Marcdante KJ, Kleigman RM, eds. Nelson Essentials of Pediatrics. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 196.

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  • Crab louse, female - illustration

    This is a photomicrograph of a female pubic louse. The condition known as crabs is so named because of the resemblance of a pubic louse to a crab. The bodies of pubic lice are shorter and rounder than those of head lice. (Image courtesy of the Centers for Disease Control and Prevention.)

    Crab louse, female

    illustration

  • Pubic louse-male - illustration

    This is a photomicrograph of a male pubic louse. The condition known as crabs is so named because of the resemblance of a pubic louse to a crab. The bodies of pubic lice are shorter and rounder than those of head lice.

    Pubic louse-male

    illustration

  • Crab lice - illustration

    This photograph shows pubic lice clinging to individual hairs (the small, whitish specks). The reddish, crusted areas with scabs (excoriated areas) are caused by scratching. (Image courtesy of the Centers for Disease Control and Prevention.)

    Crab lice

    illustration

  • Head louse and pubic louse - illustration

    This picture compares the relative size and shape of the head louse and the pubic louse.

    Head louse and pubic louse

    illustration

  • Crab louse, female - illustration

    This is a photomicrograph of a female pubic louse. The condition known as crabs is so named because of the resemblance of a pubic louse to a crab. The bodies of pubic lice are shorter and rounder than those of head lice. (Image courtesy of the Centers for Disease Control and Prevention.)

    Crab louse, female

    illustration

  • Pubic louse-male - illustration

    This is a photomicrograph of a male pubic louse. The condition known as crabs is so named because of the resemblance of a pubic louse to a crab. The bodies of pubic lice are shorter and rounder than those of head lice.

    Pubic louse-male

    illustration

  • Crab lice - illustration

    This photograph shows pubic lice clinging to individual hairs (the small, whitish specks). The reddish, crusted areas with scabs (excoriated areas) are caused by scratching. (Image courtesy of the Centers for Disease Control and Prevention.)

    Crab lice

    illustration

  • Head louse and pubic louse - illustration

    This picture compares the relative size and shape of the head louse and the pubic louse.

    Head louse and pubic louse

    illustration

 

Review Date: 10/14/2018

Reviewed By: Michael Lehrer, MD, Clinical Associate Professor, Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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