Patient education: Pubic lice (Beyond the Basics)

INTRODUCTION — There are three types of lice that infest humans (figure 1):

●The head louse

●The body louse

●The pubic louse or "crab"

Pubic lice (crabs) are most often spread from one person to another through sexual contact. Pubic lice can be found in all parts of the world, affecting men and women of all races.

This article reviews the diagnosis and treatment of pubic lice. Head lice are discussed separately (see "Patient education: Head lice (Beyond the Basics)"). More detailed information about pubic lice is available by subscription. (See "Pediculosis pubis and pediculosis ciliaris".)

PUBIC LICE DESCRIPTION — The pubic or crab louse is tiny and round. It can be difficult to see unless it is filled with blood from a recent feeding. It has crab-like claws that allow it to grasp tightly onto hair. Female lice lay up to 26 eggs (called nits) over a period of three to four weeks. The eggs hatch after about eight days.

Although these lice primarily affect the pubic area, they can also be found on other areas of the body (eyebrows, armpits, beard, mustache). Pubic lice usually are not found on the head. (See "Patient education: Head lice (Beyond the Basics)".)

Animals do not carry or spread pubic lice. However, pubic lice can move and spread from one person to another on clothing, bedsheets, towels, or other shared items.

PUBIC LICE SYMPTOMS — Most people infested with pubic lice have itching in the pubic or genital area. Other parts of the body, such as the armpits, can also be itchy if lice are present. There might be pale bluish spots on the lower belly, upper thighs, or buttocks from repeat feedings in the same area.

Children of parents infested with pubic lice occasionally develop a lice infestation of the eyelashes or eyebrows. This can cause an itching or burning sensation in the eyes, and the eyelids might look red and irritated.

PUBIC LICE DIAGNOSIS — Your doctor or nurse can diagnose pubic lice by looking at the genital area for lice or their eggs (picture 1).

If you are diagnosed with pubic lice, which is a sexually transmitted infection, you should be tested for other sexually transmitted infections, such as gonorrhea, chlamydia, syphilis, and HIV. (See "Patient education: Gonorrhea (Beyond the Basics)" and "Patient education: Chlamydia (Beyond the Basics)" and "Patient education: Testing for HIV (Beyond the Basics)".)

PUBIC LICE TREATMENT — The recommended treatment for pubic lice is a lotion or cream that is applied to the skin. The most commonly used treatments include:

●Permethrin (Nix, Rid)

●Pyrethrin (A-200, Pronto, Tisit)

Before using the treatment, your skin should be cool and dry so that it will not absorb the medicine. You should apply the lotion or cream to the skin and hair in the pubic area and skin around the anus, but not inside the vagina or rectum. Other hairy areas, such as the underarms, chest, back, and thighs should also be treated. After 10 minutes, rinse the treatment off with water.

After treatment, you can remove any lice that you see with your fingernails, a fine-toothed comb, or tweezers.

Some people need a second treatment to get rid of public lice. Your doctor or nurse may ask you to return for an exam to see if any lice remain before doing a second treatment. Alternatively, your doctor or nurse may ask you to do a second treatment 9 to 10 days after your first treatment.

Occasionally, lice infestation does not resolve despite proper use of a particular treatment. If this occurs, discuss this with your health care provider. A different treatment may be necessary.

If you are diagnosed with pubic lice, you should tell anyone that you have had sex with during the previous month to get treated. You should not have sex with your partner(s) again until both you and your partner(s) have been treated and re-evaluated to confirm that treatment was effective. You should wash any clothing, towels, and bedding used within three days before treatment in hot water and dry the items on the hottest setting. Dry cleaning is another option for cleaning clothing.

If there are items that cannot be washed or dry cleaned, you can place the item in a sealed plastic bag for two weeks.

Eyelash involvement — Eyelash infestation can occur in adolescents or adults who have pubic lice. The eyelashes can also become involved in children who are close contacts of adults with pubic lice. This condition may cause itching, burning, and eye irritation. Children with eyelash infestation may continually rub their eyes.

Children with an infestation of the eyelashes can be treated with petroleum jelly (ask a pharmacist to find petroleum jelly that is safe to use in the eyes as regular petroleum jelly may be irritating); a prescription may be necessary. You should apply the petroleum jelly to the eyelids twice a day for 8 to 10 days. The jelly will loosen the lice and nits so that you can pull them off with your fingers. In more severe cases, the child's doctor or nurse might recommend a prescription treatment.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Lice (The Basics)
Patient education: Syphilis (The Basics)
Patient education: Vulvar itching (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Head lice (Beyond the Basics)
Patient education: Gonorrhea (Beyond the Basics)
Patient education: Chlamydia (Beyond the Basics)
Patient education: Testing for HIV (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Approach to the patient with a scalp disorder
Pediculosis capitis
Pediculosis corporis
Pediculosis pubis and pediculosis ciliaris

The following organizations also provide reliable health information.

●National Library of Medicine

     (https://medlineplus.gov/ency/article/000841.htm, available in Spanish)

●Center for Disease Control and Prevention

     (https://www.cdc.gov/parasites/lice/)

●The Nemours Foundation

     (https://www.kidshealth.org/en/parents/pubic-lice.html)

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