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Pediculosis pubis - Anogenital in
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Other Resources UpToDate PubMed

Pediculosis pubis - Anogenital in

See also in: Overview
Contributors: Gabriela Ulloa MD, Loren Krueger MD, Susan Burgin MD
Other Resources UpToDate PubMed


Pediculosis pubis (pubic lice or crabs) is a highly contagious, sexually transmitted parasitic infestation with the pubic or crab louse, Phthirus pubis. Disease is most often spread from person to person by close physical contact, but it may occasionally be spread via fomites such as clothing or linens. Household pets do not play a role in transmission.

Epidemiology is difficult to elucidate as the infection is likely under-recognized and can be treated without presentation to a health care provider. However, this condition is more common in sexually active individuals. Lice live on terminal hair, typically in the pubic and perianal regions, although infestations may also be noted in the eyelashes (pediculosis palpebrarum), eyebrows, and other facial hair, as well as chest and axillary hair. Scalp infestation may also be seen in tightly curled hair. The lice are not adapted for crawling.

The incubation time is less than one week from contact, although it has been found to be longer in some cases. The eggs (nits) are cemented to hair shafts with chitin and are difficult to remove. Lice hatch in approximately 6-10 days. The lifespan of the louse is less than 1 month. The lice are not able to survive without feeding within 24 hours.

Although the bites of the lice are thought to be painless, the majority of those infected will present with extreme pruritus; one study suggests up to 86% will complain of pruritus. This is thought to be secondary to a reaction to the saliva and/or the anticoagulant injected into the skin by the louse during feeding.


B85.3 – Phthiriasis

71011005 – Pediculosis pubis

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Differential Diagnosis & Pitfalls

Most commonly, pediculosis pubis is mistaken for another form of infestation.

Pediculosis capitis and pediculosis corporis can be distinguished based on the prevailing location of the lice (pediculosis capitis is predominantly on scalp hair, while pediculosis corporis is predominantly identified on clothing) and the physical appearance of the lice (pediculosis capitis, corporis lice are more slender).

Other considerations include:
Differential diagnosis of concretions around hair shafts:
Hair shaft abnormalities such as trichorrhexis nodosa and trichorrhexis invaginata may also present with whitish adherent flecks on hair shafts. Usually scalp hair is affected. Eyebrows may also be affected in trichorrhexis invaginata.

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Last Reviewed:12/20/2017
Last Updated:12/20/2017
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Patient Information for Pediculosis pubis - Anogenital in
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Contributors: Medical staff writer


Pubic lice (pediculosis pubis), also known as crab lice or crabs, is a louse (a type of wingless, bloodsucking insect) that can live and multiply (infest) on skin that grows pubic hair. Pubic lice most commonly affect the pubic hair, but other hair-bearing areas, such as the armpits and eyelashes, eyebrows, or scalp, may also be affected. The infestation usually causes itching, but it can occur without any symptoms. It is spread by close physical contact or contaminated clothing, bedding, or towels (fomites). Pubic lice infestations may occur with other sexually transmitted diseases.

Who’s At Risk

Men are more commonly affected by public lice, possibly because they have more coarse body hair.

This infestation is most frequent between the ages of 15–40 in people who are sexually active.

Signs & Symptoms

Lice and their eggs (nits) may attach themselves to the hair in the pubic region and other areas. Lymph nodes in the groin area may be swollen. Slate blue spots may be seen at the bite sites.

Self-Care Guidelines

Always use safe sex practices, including avoidance of intimate contact with partners affected with pubic lice.

When to Seek Medical Care

See your doctor for evaluation if you think you might have pubic lice.


Your doctor may:
  • Treat the infestation with permethrin cream rinse OR pyrethrins with piperonyl butoxide. Treatment with typical insecticides may be repeated after 1 week.
  • Try malathion 0.5% lotion OR ivermectin, an oral medication, taken in one dose and repeated after 2 weeks.
  • Treat any sex partners you have had within the previous month, as recommended by the Centers for Disease Control (CDC).
Your doctor should prescribe treatment for all infested hair-bearing areas to prevent the infestation from coming back. Eyelash involvement should not be treated with the above medications; an ophthalmic ointment is used instead.

Avoid sexual contact until you and your partner(s) have been treated and reevaluated to be sure the infestation is no longer present.


Bolognia, Jean L., ed. Dermatology, pp.1326-1328. New York: Mosby, 2003.

Freedberg, Irwin M., ed. Fitzpatrick's Dermatology in General Medicine. 6th ed. pp.2286, 2287-2289. New York: McGraw-Hill, 2003.
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Pediculosis pubis - Anogenital in
See also in: Overview
A medical illustration showing key findings of Pediculosis pubis : Erythema, Hyperpigmented macule, Lice exposure, Pruritus
Clinical image of Pediculosis pubis - imageId=2074754. Click to open in gallery.  caption: 'Pubic lice and nits attached to pubic hair shafts.'
Pubic lice and nits attached to pubic hair shafts.
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