Updated January 2014

Definition

Crabs, Phthirus pubis, are small grey or brownish-red insects that live mostly in pubic hair. Occasionally they can be found in eyelashes, eyebrows, chest, armpit and facial hair.

Causes

Crabs are usually spread through sexual contact. Sometimes they can also be spread by close personal contact or contact with infested personal items such as clothing, towels, and bed linens. It is very rare for crabs to be spread by contact with a toilet seat since they can live for only 1 to 2 days off of the human body.

Anyone can get crabs, though it is most common among sexually active people and in situations where individuals are in close contact. Crabs are not related to poor hygiene or social status.

Animals cannot get or spread pubic lice.

Signs and Symptoms

Symptoms may appear right away; however if it is a mild case a person may not notice for a few weeks. The most common symptom is itching in the pubic area. Scratching can lead to sores and a possible secondary bacterial infection of the skin. Some people may notice bluish spots in the pubic area or on the inner thighs where the crabs bite. Dried spots of blood may also be found on a person’s underwear, along with fine black particles of crab feces. Live crabs or lice eggs (“nits”) may also been seen.

Diagnosis and Tests

A healthcare provider can inspect the area for crabs and small grayish-white eggs (“nits”). They can be seen with the naked eye or sometimes a magnifying glass is necessary.

A person diagnosed with crabs should consider testing for sexually transmitted infections (STIs).

Complications

Scratching and irritation of the skin can lead to secondary bacterial infections.

Treatment

Crabs will not go away without treatment. Ordinary soap and water will not kill them. Pharmacies have over the counter cream and shampoo treatments. Following treatment, the crabs will usually be killed but may leave some eggs (nits) attached to the hair shafts. Nits should be physically removed by using a fine-toothed comb or with your fingernails. Shaving alone may not get rid of the problem. Treatment should be repeated if live crabs are found 9 to 10 days later.

Clothes, bedding, and other possible contaminated items should be washed in hot water and dried at the hottest setting, dry cleaned, or put into plastic bags and sealed for two weeks. Items that cannot be washed or bagged, such as sofas, mattresses and rugs should be thoroughly vacuumed.

Prevention/Self-care Tips

Here are a few important points to remember:

  • Follow all of the instructions that come with the treatment.
  • Itching may not stop until a few days after treatment.
  • It is possible to have more than one infection at a time, so it is important to be tested for other STIs.
  • Use condoms correctly every time you have sex to lower your chance of getting an STI, including HIV.

Information for Sexual Partners

It is important for sexual partners and people who live in the same home to check for crabs. If they have crabs, they will need to be treated at the same time so that they will not re-infect you after you have completed the treatment.

Do not have sex again if you or your partner(s) have not fully completed treatment or if you are still displaying symptoms of the infection. Remember, you can become re-infected immediately after your infection clears up.

Ask your health care provider when receiving treatment about when you can have sex again.

More Information

Call the AIDS and Sexual Health InfoLine at 416-392-2437

SAFER SEX: To reduce your risk of getting a sexually transmitted infection (STI),
use a condom every time you have vaginal, anal or oral sex