Also called crab lice or “crabs,” pubic lice are parasitic insects found primarily in the pubic or genital area of humans. Pubic lice infestation is found worldwide and occurs in all races, ethnic groups, and levels of society.
What do pubic lice look like?
Pubic lice have three forms: the egg (also called a nit), the nymph, and the adult.
Nit: Nits are lice eggs. They can be hard to see and are found firmly attached to the hair shaft. They are oval and usually yellow to white. Pubic lice nits take about 6–10 days to hatch.
Nymph: The nymph is an immature louse that hatches from the nit (egg). A nymph looks like an adult pubic louse but it is smaller. Pubic lice nymphs take about 2–3 weeks after hatching to mature into adults capable of reproducing. To live, a nymph must feed on blood.
Adult: The adult pubic louse resembles a miniature crab when viewed through a strong magnifying glass. Pubic lice have six legs; their two front legs are very large and look like the pincher claws of a crab. This is how they got the nickname “crabs.” Pubic lice are tan to grayish-white in color. Females lay nits and are usually larger than males. To live, lice must feed on blood. If the louse falls off a person, it dies within 1–2 days.
Where are pubic lice found?
Pubic lice usually are found in the genital area on pubic hair; but they may occasionally be found on other coarse body hair, such as hair on the legs, armpits, mustache, beard, eyebrows, or eyelashes. Pubic lice on the eyebrows or eyelashes of children may be a sign of sexual exposure or abuse. Lice found on the head generally are head lice, not pubic lice.
Animals do not get or spread pubic lice.
What are the signs and symptoms of pubic lice?
Signs and symptoms of pubic lice include
- Itching in the genital area
- Visible nits (lice eggs) or crawling lice
How did I get pubic lice?
Pubic lice usually are spread through sexual contact and are most common in adults. Pubic lice found on children may be a sign of sexual exposure or abuse. Occasionally, pubic lice may be spread by close personal contact or contact with articles such as clothing, bed linens, or towels that have been used by an infested person. A common misconception is that pubic lice are spread easily by sitting on a toilet seat. This would be extremely rare because lice cannot live long away from a warm human body and they do not have feet designed to hold onto or walk on smooth surfaces such as toilet seats.
How is a pubic lice infestation diagnosed?
A pubic lice infestation is diagnosed by finding a “crab” louse or egg (nit) on hair in the pubic region or, less commonly, elsewhere on the body (eyebrows, eyelashes, beard, mustache, armpit, perianal area, groin, trunk, scalp). Pubic lice may be difficult to find because there may be only a few. Pubic lice often attach themselves to more than one hair and generally do not crawl as quickly as head and body lice. If crawling lice are not seen, finding nits in the pubic area strongly suggests that a person is infested and should be treated. If you are unsure about infestation or if treatment is not successful, see a health care provider for a diagnosis. Persons infested with pubic lice should be investigated for the presence of other sexually transmitted diseases.
Although pubic lice and nits can be large enough to be seen with the naked eye, a magnifying lens may be necessary to find lice or eggs.
Control And Prevention
The following are steps that can be taken to help prevent and control the spread of pubic (“crab”) lice:
- All sexual contacts of the infested person should be examined. All those who are infested should be treated.
- Sexual contact between the infested person(s)s and their sexual partner(s) should be avoided until all have been examined, treated as necessary, and reevaluated to rule out persistent infestation.
- 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.
Persons with pubic lice should be examined and treated for any other sexually transmitted diseases (STDs) that may be present.
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% (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.
Both topical and oral ivermectin have been used successfully to treat lice; however, only topical ivermectin lotion currently is approved by the U.S. Food and Drug Administration (FDA) for treatment of lice. Oral ivermectin is not FDA-approved 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.)
- Wash the infested area; towel dry.
- 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.
- Following treatment, most nits will still be attached to hair shafts. Nits may be removed with fingernails or by using a fine-toothed comb.
- Put on clean underwear and clothing after treatment.
- 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 2–3 days before treatment. Use hot water (at least 130°F) and the hot dryer cycle.
- Items that cannot be laundered can be dry-cleaned or stored in a sealed plastic bag for 2 weeks.
- All sex partners from within the previous month should be informed that they are at risk for infestation and should be treated.
- Persons should avoid sexual contact with their sex partner(s) until both they and their partners have been successfully treated and reevaluated to rule out persistent infestation.
- Repeat treatment in 9–10 days if live lice are still found.
- Persons with pubic lice should be evaluated for other sexually transmitted diseases (STDs).
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 2–4 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.