Pediculosis pubis is an infection of the genital area caused by the crab louse (Phthirus pubis). The lice (commonly called crabs) are small bugs that are visible to the naked eye without the aid of a magnifying glass or microscope. The lice live on pubic hair (or any other hair) and are associated with itching.

The treatment for pubic lice is usually with a 1% cream rinse of permethrin that is applied to the affected area and washed off after 10 minutes. Alternative treatments include a 1% shampoo of lindane applied for 4 minutes before washing off or pyrethrins with piperonyl butoxide applied for 10 minutes before washing off.

What are pubic lice?

Also called "crabs," pubic lice are parasitic insects found in the genital area of humans. Infection is common and found worldwide.

How did I get pubic lice?

Pubic lice are usually spread through sexual contact. Rarely, infestation can be spread through contact with an infested person's bed linens, towels, or clothes. A common misbelief is that infestation can be spread by sitting on a toilet seat. This isn't likely, since lice cannot live long away from a warm human body. Also, lice do not have feet designed to walk or hold onto smooth surfaces such as toilet seats. Infection in a young child or teenager may indicate sexual activity or sexual abuse.

Where are pubic lice found?

Pubic lice are generally found in the genital area on pubic hair; but may occasionally be found on other coarse body hair, such as hair on the legs, armpit, mustache, beard, eyebrows, and eyelashes. Infestations of young children are usually on the eyebrows or eyelashes. Lice found on the head are not pubic lice; they are head 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

What do pubic lice look like?

There are three stages in the life of a pubic louse: the nit, the nymph, and the adult.

Nit: Nits are pubic lice eggs. They are hard to see and are found firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about 1 week to hatch.

Nymph: The nit hatches into a baby louse called a nymph. It looks like an adult pubic louse, but is smaller. Nymphs mature into adults about 7 days after hatching. To live, the 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, but their two front legs are very large and look like the pincher claws of a crab; this how they got the nickname "crabs." Pubic lice are tan to greyish-white in color. Females lay nits; they are usually larger than males. To live, adult lice need to feed on blood. If the louse falls off a person, it dies within 1-2 days.

How is a pubic lice infestation diagnosed?

A lice infestation is diagnosed by looking closely through pubic hair for nits, nymphs, or adults. It may be difficult to find nymph or adult; here are usually few of them and they can move quickly away from light. If crawling lice are not seen, finding nits confirms 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.

How are pubic lice treated?

A lice-killing shampoo (also called a pediculicide) made of 1% permethrin or pyrethrin is recommended to treat pubic lice. These products are available without a prescription at your local drug store. Medication is generally very effective; apply the medication exactly as directed on the bottle. A prescription medication, called Lindane (1%) is available through your health care provider. Lindane is not recommended for pregnant or nursing women, or for children less than 2 years old.

Malathion* lotion 0.5% (Ovide*) is another prescription medication that is effective against pubic lice.

None of these treatments should be used for involvement near the eyes because they can be very irritating. The patient's bedding and clothing should be machine-washed with hot water. All sexual partners within the preceding month should be treated for pubic lice and evaluated for other STDs.

How to treat pubic lice infestations

Wash the infested area; towel dry. Thoroughly saturate hair with lice medication. If using permethrin or pyrethrins, leave medication on for 10 minutes; if using Lindane, shampoo should only be left on for 4 minutes. Thoroughly rinse off medication with water. Dry off with a clean towel. Following treatment, most nits will still be attached to hair shafts. Nits may be removed with fingernails.

• Put on clean underwear and clothing after treatment.
• To kill any lice and nits that may be left on clothing or bedding, machine wash those washable items that the infested person used during the 2-3 days before treatment. Use the hot water cycle (130o F) of the washing machine to wash clothes. Use the hot cycle of the dryer for at least 20 minutes to dry clothes.
• Dry clean clothing that is not washable.
• Inform any sexual partners that they are at risk for infestation.
• Do not have sex until treatment is complete.
• Do not have sex with infected partners until partners have been treated and infestation has been cured.
• Retreat in 7-10 days if lice are still found.

To treat nits and lice found on eyebrows or eyelashes

• If only a few nits are found, it may be possible to remove live lice and nits with your fingernails or a nit comb.
• If additional treatment is needed for pubic lice nits found on the eyelashes, applying an ophthalmic- grade petrolatum ointment (only available by prescription) to the eyelids twice a day for 10 days is effective.