Crabs (Pubic lice)

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Crabs (also known as pubic lice) are small parasites that feed on human blood. Crabs are usually found on the pubic hair, but can also be found on other parts of the body where a person has coarse hair (such as armpits, eyelashes, and facial hair). Crabs rarely infest head hair.

Anyone can get crabs. Having crabs does not mean a person in unclean or dirty. The most noticeable symptom of crabs is itching. The itching usually starts about 5 days after a person gets crabs.

There are several treatments for crabs. Some treatments require a prescription, while others do not. The only way to prevent infestation with crabs is avoid contact with infested people, bed linens, clothing, and furniture.

FAQs

What is crabs?

Crabs, or pubic lice, is an infestation of crab-like parasites that attach themselves to pubic hair and other course hair on the body. While the scientific name for the parasite is Pthirus pubis and the scientific name for the condition is Pediculus Pubis, both are referred to as crabs. Although crabs come from the same family of parasites as head and body lice, they are not the same thing. While crabs need blood to survive, they can live up to 24 hours off a human body.

Crabs have three very distinct phases:


  • The first phase is the egg, or nit.
  • The second phase is the nymph, or immature form of the adult.
  • The third phase is the louse, or adult crab.

How common is it?

In the United States, there are an estimated 3 million cases of crabs every year.


How is it transmitted?

Sexual Transmission: Most cases of crabs are transmitted through sexual contact, when the crabs move from the pubic hair of one person to the pubic hair of another. Even when there is no sexual penetration, you can get crabs or transmit crabs to someone else. You can get crabs whenever some part of your body that has coarse hair (such as the pubic area, eyelashes, eyebrows, facial hair, chest, or armpits) comes into contact with the infested pubic or other course hair. Crabs do not usually attach to head hair.

Nonsexual Transmission: Nonsexual transmission of crabs is also possible. A person can get crabs from:

  • sleeping in an infested bed or using infested towels.
  • wearing infested clothing.
  • an infested toilet seat, though this is rare.

What are the symptoms?

  • The most common symptom of crabs is itching in the pubic area. This itching is caused by an allergic reaction to the bites, and usually starts about five days after a person gets crabs.
  • A person may be able to see individual crabs by looking closely or using a magnifying glass. Crabs are small parasites that resemble crabs you see on the beach. They may be whitish-gray or rust colored.
  • A person may also notice crab eggs, or nits, attached to the base of the hair (close to where it comes out of your body). Nits are small, oval-shaped and pearl-like in color.
  • Dark or bluish spots can appear and last for several days in the infested area; these are also a result of the bites.
  • Crabs are usually found in the pubic area. However, crabs can also be found in the armpits, eyelashes, beard/mustache and other course hair. Sometimes, though rarely, crabs are found in the hair on a person's head.

How are crabs diagnosed?

You can usually see the crabs yourself if you look closely enough. You might need a magnifying glass to help you identify them. If you are uncertain, have a health care provider examine you. He or she may need to use a microscope.


How are crabs treated?

Recommended treatments include:

Permethrin cream:

  • The cream can be applied to the affected area and washed off after 10 minutes.
  • Permethrin is available over the counter.
  • Should not be used for treatment of eyelashes or eyebrows.

Lindane shampoo (Kwell®)

  • A shampoo that is applied to the affected area and thoroughly washed off after 4 minutes.
  • Available only by prescription.
  • Should not be used for treatment of eyelashes or eyebrows.
  • NOTE: Lindane (Kwell®) is potentially harmful and may cause central nervous system complications, even though no problems have been known to occur in treatments limited to the recommended 4-minute period.
  • Should not be used on broken skin.
  • Not recommended to be used by the following people:
    • women who are pregnant or lactating
    • children under 2 years of age
    • people with seizure disorders
    • people with extensive dermatitis or known allergies to any ingredients found in Lindane

Pyrethrins with piperonyl butoxide

  • This shampoo is applied to the affected area and washed off after 10 minutes.
  • Available over the counter.
  • Should not be used for treatment of eyelashes or eyebrows.

For infested eyelids and eyebrows an ointment is available by prescription.

Even if treatment for crabs is successful, you may still have some itching as a result of a skin irritation or allergic reaction. If so, you can use hydrocortisone cream to help stop the itching.


What else can I do to get rid of crabs?

  • Even after treatment, most nits or eggs will remain attached to the hair. Nits can be removed with fingernails or a fine-tooth comb.
  • Wear clean clothing and sleep between freshly laundered bed linens after treatment.
  • Notify sex partners so that they can be treated.
  • Abstain from sex until treatment is successful and all partners have been treated.
  • After you are treated, your clothes and bedding may still be infested with crabs. To get rid of them, you will want to wash all your clothes, bed linens, sleeping bags, etc. in hot water (at least 130-degrees F). Dry on hot cycle for at least 20 minutes.
  • Items that cannot be washed can be placed in a plastic bag for two weeks or dry-cleaned to ensure decontamination.
  • It is not necessary to decontaminate furniture or fumigate living areas. If desired, furniture can be vacuumed or treated with a bug spray containing an agent active against crabs.
  • If after about a week you still see lice, do the treatment again. Make sure that all bedding and clothing have been washed and dried on a hot cycle, dry-cleaned or decontaminated in a plastic bag for two weeks. Also make sure that that sex partners have been treated.
  • Contact your health care provider if treatment still does not work.

What does it mean for my health?

Crabs, in general, does not cause anything more than discomfort and inconvenience. Occasionally, secondary bacterial infections may occur due to aggressive scratching.


How can I reduce my risk?

As with other sexually transmitted infections (STIs) there are things people can do to reduce or eliminate the risk of infection with chancroid. These include the following:

  • Abstinence(not having sex) is a sure way to avoid infection.
  • Mutual monogamy with an uninfected partner (having sex with only one partner who only has sex with you) is another way of reducing risk. Limiting the number of sex partners can also reduce risk as it would for all STIs.
  • Although latex condoms do not provide effective protection against crabs, condom use is effective in preventing other STIs.

How do I tell my partner?

Telling a partner can be hard. If you find out you have crabs, it is important that you talk to your partner as soon as you can so she or he can get treatment. It is possible to pass crabs back and forth. If you get treated and your partner doesn't, you may get infected again.