Page header image

Pubic Lice (Crab Lice)

What are pubic lice?

Pubic lice, also called crab lice, are tiny wingless insects that look like crabs when viewed with a microscope. They are 1 to 3 millimeters long, or less than 1/8 inch. They live in hairy areas of the human body (usually the pubic hair).

Lice bite through the skin to suck blood. They also lay eggs and attach them to hairs. These eggs, called nits, hatch in 8 to 10 days, producing more lice.

How do people get crab lice?

Crab lice are passed from person to person through close body contact. The lice can live for 1 to 2 weeks away from the body, so you can get the lice from such items as bed sheets, towels, and sleeping bags.

What are the symptoms?

The most common symptom is itching. At first, however, when you have only a few lice, you may have no symptoms.

You may see one or more lice or nits in your pubic hair. The nits look like tiny white dots attached to a hair. They look like dandruff. Dandruff, however, is easily brushed out of the hair. Nits cannot be brushed or flicked off. They must be pulled off the hair with your fingers.

Crab lice sometimes live in other hairy areas, such as the chest, abdomen, underarms, and head. They may even be in facial hair, such as beards, eyebrows, and eyelashes.

How is it diagnosed?

Your health care provider looks for lice or nits in your pubic hairs or on other parts of your body.

How is it treated?

An antilice shampoo is used to get rid of the lice. You can get the shampoo without a prescription at a drugstore or pharmacy. The shampoo should have 1% permethrin or pyrethrin in it, such as Nix or RID shampoo. There is also a prescription medicine called lindane that your health care provider may prescribe. (Lindane should not be used by women who are pregnant or breast-feeding or by children under 2 years.)

To use the shampoo:

  1. Put the lice-killing shampoo on the pubic hair when the hair is dry. Make sure all the hair is wet with the product.
  2. Leave the medicine on for the number of minutes required on the package instructions.
  3. Rinse with thoroughly with warm water and rub with a dry towel.
  4. Comb the pubic hair thoroughly with a fine-tooth comb to remove any remaining nits. You can also remove nits with your fingernails.
  5. Put on clean underwear and clothes after the treatment.
  6. A second treatment must be done in 7 to 10 days to kill any newly hatched lice.

Do not have sex until you have completed the treatment and the lice and nits are all gone. You need to remove lice from your clothing, towels, and bedding. Machine wash all items that you used in the last 3 days before you started treatment. Use the hot water cycle to wash the items. Use the hot setting on your dryer for at least 20 minutes to dry the laundry. Anything that can't be washed this way needs to be dry cleaned. Contaminated clothing that cannot be washed or dry cleaned should be sealed in a plastic bag for 2 weeks to ensure death of nits.

What can be done to help prevent crab lice?

Tell your sexual partner about the crab lice because he or she may also be infested. Since these infestations spread easily, all members of your household should also be examined carefully. Anyone who has lice should be treated promptly to avoid spreading the lice to others.

The best way to prevent crab lice is to have one sexual partner or avoid sexual contact. Condoms are not good protection against crab lice because they do not cover the hairy areas where the lice live. You should also avoid contact with contaminated clothing, bed clothing, and toilet seats.

Developed by David W. Kaplan, MD, and McKesson Provider Technologies.
Published by McKesson Provider Technologies.
Last modified: 2006-05-17
Last reviewed: 2005-04-27
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright 2006 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.
Page footer image