Pubic lice

Definition

Pubic lice are small, six-legged creatures that infect the pubic hair area and lay eggs. These lice can also be found in armpit hair and eyebrows.

Alternative Names

Pediculosis - pubic lice; Lice - pubic; Crabs

Causes, incidence, and risk factors

Pubic lice are known as Phthirus pubis. Lice infestation is found mostly in teenagers and usually spreads during sexual activity.

Sometimes, pubic lice can spread through contact with objects such as toilet seats, sheets, blankets, or bathing suits at a store. However, this type of spreading is rare.

Animals cannot spread lice to humans.

Other types of lice include:

  • Body lice (Pediculus humanus corporis)
  • Head lice (Pediculus humanus capitis)

Risk factors include:

  • Having multiple sexual partners
  • Having sexual contact with an infected person
  • Sharing bedding or clothing with an infected person

Symptoms

Almost anyone with pubic lice will have itching in the area covered by pubic hair (it often gets worse at night). This itching may start soon after getting infected with lice, or it may not start for up to 2 - 4 weeks after contact.

Other symptoms:

  • Skin reaction that is bluish-gray in color
  • Sores (lesions) in the genital area due to bites and scratching

Signs and tests

An examination of the outer genital area shows small gray-white oval eggs (nits) attached to the hair shaft. It may also reveal adult lice. The health care provider might also see scratch marks or signs of an infection, such as impetigo.

Because pubic lice may cause an eye infection (blepharitis) in young children, their eyelashes should be examined for evidence of lice with a high-powered magnifying glass.

Adult lice may be easily identified under the microscope. Their crab-like appearance is the reason that pubic lice are referred to as "the crabs."

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

Treatment

Pubic lice are best treated with a prescription wash containing permethrin, such as Elimite or Kwell:

  • Thoroughly work the shampoo into the pubic hair and surrounding area for at least 5 minutes.
  • Rinse well.
  • Comb the pubic hair with a fine-toothed comb to remove eggs (nits). Applying vinegar to pubic hair before combing may help loosen nits, but the hair should be dry when applying the shampoo.

A single treatment is all that is usually needed. If another treatment is recommended, it should be done 4 days to 1 week later.

Over-the-counter medications for the treatment of lice include Rid and Nix. Malathione lotion is another treatment option.

While you are treating pubic lice, wash all clothing and linens in hot water. Items that cannot be washed may be sprayed with a medicated spray or sealed (suffocated) in plastic bags and not used for 10 - 14 days. It is important for all intimate contacts to be treated at the same time.

People with pubic lice should be evaluated for other sexually-transmitted infections at the time of diagnosis.

Support Groups

Expectations (prognosis)

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

Complications

The constant scratching and digging can cause the skin to become raw, and secondary infections may develop.

Calling your health care provider

Call for an appointment with your health care 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 infected people. If you are sexually active, use safe sex practices to avoid getting lice.

Good personal hygiene is always recommended. If possible, avoid trying on bathing suits while you are shopping. However, if you must try them on, be sure to wear your underwear. This may prevent transmission.

References

Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa:Mosby Elsevier;2009: pp 590-594.

Diaz JH. Lice (pediculosis). In: Mandell GL, Bennett JE, Dolin R. Mendell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa:Churchill Livingstone Elsevier;2009:chap 293.