What are crabs?

Crabs are parasites. Crabs are often referred to as pubic lice and are not to be confused with body lice. The scientific name for crabs is Pediculus pubis. Crabs need blood to survive, but they can live up to 24 hours off a human body. Crabs have three very distinct phases; egg, nit (egg or young louse), and adult louse. The louse is the stage of the parasite that causes itching. Louse is the singular for lice (like mouse and mice).

How common are they?

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

How do people get crabs?

Sexual transmission - You can get crabs when you have skin-to-skin contact with another person. Even when there is no sexual penetration, you can get (or give) crabs.

Non-sexual transmission - You can get crabs from sleeping in an infested bed or using infested towels.

Pubic lice found on children may be a sign of sexual exposure or abuse.

Animals do not get or spread lice.

What are the signs or symptoms of crabs?

  • The most common symptom of crabs is itching in your pubic area. The itching is caused by an allergic reaction to the bites, and usually starts about five days after you get crabs.
  • If you have crabs and look closely enough in your pubic area, you may see small crab-like parasites that may be whitish-gray or rust colored.
  • Crab eggs are small and oval-shaped. They are attached to the base of the hair (close to where it comes out of your body).
  • Crabs are usually found in your pubic area; however, you may find them in your armpits, eyelashes, beard/mustache and sometimes in the hair on your head.

How are crabs diagnosed?

You can usually see the crabs yourself if you look closely enough. The adult pubic louse resembles a miniature crab which has six legs, but their two front legs are very large and look like the pincher claws of a crab; this is how they got the nickname “crabs.” 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.

What is the treatment for crabs?

A lice-killing lotion containing 1 percent permethrin or a mousse containing pyrethrins and piperonyl butoxide can be used to treat pubic ("crab") lice. These products are available over-the-counter without a prescription at a local drug store or pharmacy. These medications are safe and effective when used exactly according to the instructions in the package or on the label.

Lindane shampoo is a prescription medication that can kill lice and lice eggs. However, lindane is not recommended as a first-line therapy. Lindane can be toxic to the brain and other parts of the nervous system; its use should be restricted to patients who have failed treatment with or cannot tolerate other medications that pose less risk. Lindane should not be used to treat premature infants, persons with a seizure disorder, women who are pregnant or breast-feeding, persons who have very irritated skin or sores where the lindane will be applied, infants, children, the elderly, and persons who weigh less than 110 pounds.

Malathion* lotion 0.5 percent (Ovide*) is a prescription medication that can kill lice and some lice eggs; however, malathion lotion (Ovide*) currently has not been approved by the U.S. Food and Drug Administration (FDA) for treatment of pubic ("crab") lice.

Ivermectin has been used successfully to treat lice; however, ivermectin currently has not been approved by the U.S. Food and Drug Administration (FDA) for treatment of lice.

How to treat pubic lice infestations: (Warning: See special instructions for treatment of lice and nits on eyebrows or eyelashes. The lice medications described in this section should not be used near the eyes.)

  1. Wash the infested area; towel dry.
  2. Carefully follow the instructions in the package or on the label. Thoroughly saturate the pubic hair and other infested areas with lice medication. Leave medication on hair for the time recommended in the instructions. After waiting the recommended time, remove the medication by following carefully the instructions on the label or in the box.
  3. Following treatment, most nits will still be attached to hair shafts. Nits may be removed with fingernails or by using a fine-toothed comb.
  4.  Put on clean underwear and clothing after treatment.
  5. To kill any lice or nits remaining on clothing, towels or bedding, machine wash and machine dry those items that the infested person used during the two to three days before treatment. Use hot water (at least 130 degrees F) and the hot dryer cycle.
  6.  Items that cannot be laundered can be dry-cleaned or stored in a sealed plastic bag for two weeks.
  7.  All sex partners from within the previous month should be informed that they are at risk for infestation and should be treated.
  8.  Persons should avoid sexual contact with their sex partner(s) until both they and their partners have been successfully treated and re-evaluated to rule out persistent infestation.
  9.  Repeat treatment in nine to ten days if live lice are still found.
  10.  Persons with pubic lice should be evaluated for other sexually transmitted diseases.

Special instructions for treatment of lice and nits found on eyebrows or eyelashes:

  • If only a few live lice and nits are present, it may be possible to remove these with fingernails or a nit comb.
  • If additional treatment is needed for lice or nits on the eyelashes, careful application of ophthalmic-grade petrolatum ointment (only available by prescription) to the eyelid margins two to four times a day for 10 days is effective. Regular petrolatum (e.g., Vaseline)* should not be used because it can irritate the eyes if applied.

After you are cured, you may still have some itching as a result of a skin irritation or allergic reaction. If so, you can use hydrocortisone cream. Clothes and other items that cannot be washed can be placed in a plastic bag for two weeks. Repeat treatment in seven to ten days if lice are still found.

How can crabs be prevented?

Pubic ("crab") lice most commonly are spread directly from person to person by sexual contact. Pubic lice very rarely may be spread by clothing, bedding or a toilet seat.

  • Abstinence (not having sex).
  • Mutual monogamy (having sex with only one uninfected partner).
  • Limit the number of sex partners to reduce your risk of all STDs.
  • Use latex condoms for all types of sexual penetration (oral, vaginal, anal). Note: Latex condoms, when used consistently and correctly, can reduce the risk of transmission of other STDs, but are not considered effective against crabs.
  • Know your partner(s). Careful consideration and open communication between partners may protect all partners involved from infection.
  • Have regular check-ups if you are sexually active.
  • If you have an STD, don't have sex (oral, vaginal, or anal) until all partners have been treated.
  • Machine wash and dry clothing worn and bedding used by the infested person in the hot water (at least 130°F) laundry cycle and the high heat drying cycle. Clothing and items that are not washable can be dry-cleaned OR sealed in a plastic bag and stored for 2 weeks.
  • Do not share clothing, bedding, and towels used by an infested person.
  • Do not use fumigant sprays or fogs; they are not necessary to control pubic ("crab") lice and can be toxic if inhaled or absorbed through the skin.
  • Prompt, qualified, and appropriate medical intervention and treatment and follow-up are important steps in breaking the disease cycle.

Why should I worry about having crabs?

You may get a secondary infection as a result of scratching.

Should I tell my partner?

Yes. Telling a partner can be hard. It's important that you talk to your partner as soon as possible so she or he can get treatment. Also, it is possible to pass crabs back and forth. If you get treated and your partner does not, you may get infected again. You will need to wash all clothes, sheets and towels in hot water (at least 130-degrees F).

Should I tell my healthcare provider that I had crabs?

Yes. If you have one sexually transmitted disease, you may be at risk for others. You may want to ask your doctor or nurse about being tested for other STDs.

Where can I get more information?

Illinois Department of Public Health

HIV/STD Hotline 800-243-2437 (TTY 800-782-0423)

U.S. Centers for Disease Control and Prevention (CDC)
CDC-INFO Hotline (7am-7pm Mon.-Fri. Closed Holidays)

STD information and referrals to STD Clinics
800-CDC-INFO (800-232-4636)
TTY: 888-232-6348
In English, en Español

CDC National Prevention Information Network (NPIN)
P.O. Box 6003
Rockville, MD 20849-6003
888-282-7681 Fax

American Social Health Association (ASHA)
P. O. Box 13827
Research Triangle Park, NC 27709-3827

May 2013

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idph online home

Illinois Department of Public Health
535 West Jefferson Street
Springfield, Illinois 62761
Phone 217-782-4977
Fax 217-782-3987
TTY 800-547-0466
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