Pubic Lice

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Pubic Lice : Background Pubic Lice : Treatment
Pubic Lice : Risk Factors Pubic Lice : Prevention
Pubic Lice : Signs and Symptoms Pubic Lice : Prognosis
Pubic Lice : Complications Pubic Lice : References
Pubic Lice : Diagnosis


Pubic LicePubic lice, commonly known as “crabs”, are tiny parasites that attach themselves to the skin and hair in the genital area. Occasionally, they can also be found in armpit hair and eyebrows. The scientific name for the parasite is pthirus pubis. Pubic lice are a different type of lice than head lice or body lice. Measuring about 1.6 millimeters in diameter (the size of a pinhead), they received their nickname because their bodies resemble tiny sea crabs.

Pubic lice are most commonly spread during sexual intercourse, although they can also be spread through other types of intimate skin-to-skin contact. Very rarely, they are spread from contact with contaminated bedding, towels, clothing, or upholstered furniture. There is a common myth that public lice can be acquired by sitting on a toilet seat, but this is extremely rare since lice cannot live long away from a warm human body and do not have feet designed to hold onto a smooth surface such as a toilet seat.

The Centers for Disease Control (CDC) does not keep track of pubic lice cases, although from an analysis of medication purchases, it is estimated that there are about three million new cases each year in the United States. However, since many people don’t seek treatment, the actual number of cases may be even higher.

Pubic lice are most common in teenagers. Pubic lice in children may be a sign of sexual exposure or abuse. However, in some cases, children can become infected merely by sharing a bed with their infected parents.

When viewed through a strong magnifying glass, pubic lice resemble miniature crabs. They are tan to grayish-white in color and have six legs. The front two legs are very large and look like pincer claws. Females lay eggs (also called nits), which are oval-shaped and usually whitish in color. After about 6-10 days, the eggs hatch into nymphs, which are smaller, immature lice. Nymphs mature into adults after 2-3 weeks. In order to live, nymphs must feed on blood. If a nymph falls off a person, it dies within 1-2 days.

Risk Factors

Pubic lice is found worldwide and occurs in all races, ethnic groups, and socioeconomic classes. It is most common in people who have sex with multiple partners and who have sex as adolescents.

People who have other sexually transmitted infections are more likely to also have pubic lice.

Signs and Symptoms

Symptoms usually appear about 5 days after exposure, although some people have no symptoms at all. The most common symptom is itching or burning in the area covered by pubic hair. The itching often gets worse at night when the lice are biting and feeding. Other symptoms may include sores in the genital area, mild fever, fatigue, irritability, and the presence of lice or nits in the pubic hair.


A pubic lice infection can sometimes cause minor complications. If bites are scratched too vigorously, the wounds can become infected. Two possible infections are impetigo (a contagious bacterial infection characterized by blisters or sores) and furunculosis (an infection of the hair follicle characterized by boils, or pus-filled bumps). Some people develop discolored skin, with pale blue spots where the lice have been feeding continually. Children who have pubic lice on their eyelashes may develop a type of pink eye (conjunctivitis).


Unlike many other sexually transmitted diseases, it is usually not necessary to go to a doctor or health care professional in order to determine if you are infected. Pubic lice and eggs can be large enough to be seen with the naked eye, although usually a magnifying glass is necessary. Adult lice are tan to grayish-white in color and look like tiny crabs. You may see them crawling through the pubic hair, but since they tend to crawl more slowly than head or body lice, movement may not be visible. The eggs (nits) are whitish in color and are found in small clumps near the hair roots.


There are a variety of effective over-the counter treatments, including lice-killing lotions containing 1% permethrin and mousses containing pyrethrins and piperonyl butoxide. Some common brand names are A-200, RID, and Nix. Products should be applied according to instructions in the package or on the label. Following treatment, nits may still be attached to hair shafts and can be removed carefully with fingernails or a fine-toothed comb. Treatments may need to be repeated in seven to 10 days if live lice are found.

If over-the-counter products don’t work, stronger prescription medications are available. Some of the most common prescription medications are malathion (Ovide), a lotion, and ivermectin (Stromectol), an oral medication. Lindane, a topical treatment, is sometimes prescribed when other treatments fail, but has strong toxicity and is not recommended for pregnant women, breastfeeding women, or children younger than age 2.

If lice or nits are found in the eyebrows, it may be possible to gently remove them with a fingernail, tweezers, or nit comb. However, in many cases, a prescription ophthalmic ointment containing petrolatum is recommended. Regular petroleum jelly (Vaseline) should not be used since it can irritate the eyes if it comes in contact.

All sexual partners and anyone who may have been exposed to public lice should be treated at the same time in order to avoid re-infection. Sexual intercourse should be avoided until treatment is complete. People with pubic lice should also be evaluated for other sexually transmitted diseases.

Over-the-counter and prescription medications are only the first part of a successful treatment program. Lice that may remain in clothing and the environment must be killed as well. All bedding, towels, and clothing that may have been exposed should be thoroughly washed with hot, soapy water and dried on high heat for at least 20 minutes. Unwashable items should be dry cleaned, sprayed with a medicated spray, or sealed in an airtight bag for at least two weeks. The entire home should be thoroughly vacuumed.

Hot baths, shaving pubic hair, and other home remedies are not effective ways to treat pubic lice.


Birth control methods – including condoms – do not protect against pubic lice. The only thing that can reduce the risk is to abstain from oral, vaginal, and anal sex or to have a mutually monogamous relationship with an uninfected sex partner.

Avoid having sexual contact or sharing bedding or clothing with anyone who has an infestation. Do not resume until treatment is complete.


In general, pubic lice do not cause anything more than embarrassment, discomfort, and inconvenience. Although secondary infections sometimes occur due to vigorous scratching, the infestation is unlikely to cause any lasting health concerns. However, it is still important to be aware of treatment options and to consider prevention techniques such as mutual monogamy.


1) Pubic Lice (Crabs)
Source: Planned Parenthood Association

2) Pubic Lice

3) Pubic Lice Infestation
Source: Centers for Disease Control and Prevention

4) Pubic Lice: What They Are, How They Spread

5) Pubic Lice (Crabs)
Source: Mayo Clinic

Posted in STI.