WSU Extension


Caption: Pubic louse (crabs, crab lice)
Photo by: Ken Grey
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Pubic lice (crabs, crab lice)

(revision date: 9/3/2015)

Use Integrated Pest Management (IPM) for successful pest management.

The pubic or crab louse is an insect pest of humans spread almost exclusively by intimate or sexual contact. That said, it is possible to become infested from contact with contaminated clothing or bedding, but the most common non-sexual infestations occur when using public toilets. This is less likely, however, as crab lice do not survive long without a human host, usually less than 24 hours. Crab lice feed on human blood. Typically crab lice live and feed in the pubic and perianal region, often causing itching and irritation, sometimes with a blue dotted rash. Small black or rust-colored specks of louse feces in the underwear can also be a sign of infestation. Crab lice may be found as adult insects, nymphs or immature insects, or eggs (nits). Adult lice are usually found in the pubic area on or near the skin where they feed. Adult lice can crawl quickly, but do not fly or jump. Eggs or nits are found near the base of the hair shafts. Occasionally crab lice have been found on other coarse body hairs, such as armpit hairs, beards, or eyebrows. Adult insects range in color from pinkish-tan to grayish-white. They are about as long as they are wide, typically about 1-2 mm in length (around 1/16”). They are broadly oval and flattened in appearance. Nymphs resemble adults, but may be somewhat smaller. The oval, yellowish to white eggs are the easiest stage to find, as they are not mobile but are cemented tightly to the hair shaft near the base of the hair. The empty egg case will remain attached to the hair after hatching, making it difficult to determine if the infestation has been eliminated. However, nits further than 1/4” from the skin have usually either hatched or are dead. Use a lice comb or pick nits off with your fingernails. Keep in mind that nits are very difficult to remove but need to be removed to stop the infestation.
Management Options

Non-Chemical Management
  • Daily manual nit removal is an important part of controlling a lice infestation, even if chemical controls are used as well. Remove nits from hair with fingernails or a lice comb. Follow all instructions provided with the comb for best success. Thoroughly clean comb with soap and hot water after each use.
  • Avoid unsanitary, crowded conditions where you may come into intimate contact with infested items.
  • If public toilets are used, wipe down toilet seats thoroughly before use.
  • Avoid close contact with infested individuals, particularly at night when lice are more active and likely to wander to a new host. Bed or sexual partners of infested persons should also be checked for pubic lice.
  • Change and launder clothing frequently, particularly underwear, nightwear, and bedding. Wash all clothing and bedding items in hot water and dry in a hot dryer if possible. This may need to be repeated several times during the treatment period to control newly-hatched lice. Dry-cleaning is also effective.
  • Space and bedding sprays are not recommended for lice control, as adult lice seldom survive longer than 1-2 days away from the human host. Space and bedding sprays also do not kill the nits on fallen hairs, which can simply be removed by vacuuming or laundering in hot water.
  • Items that cannot be washed may be sealed in plastic bags for at least two weeks. Pubic lice require human blood for survival and will not survive longer than about 24 hours without a host. Nits are somewhat more durable, but most typically hatch within two weeks.
  • Human lice are not parasites of pets, nor are they spread by pets. No treatment is necessary for cats, dogs, or other household pets.
Select non-chemical management options as your first choice!

Chemical Management

For chemical treatment of lice, read and follow all label instructions carefully and completely. Be aware that some lice have become resistant to chemical controls, so use chemicals as a last resort, and ALWAYS use them along with other control measures to prevent reinfestation. When using chemical-based shampoo treatment products, treat all infested individuals of a household at the same time. DO NOT treat uninfested members of the household, as it will not stop an infestation from occurring and is unnecessary. Do not use these products on eyebrows, lashes, or near eyes. DO NOT use chemical controls if open sores are present. ADULT LICE do not die immediately after treatment; it may take as long as 8 to 12 hours. NITS may not be affected by chemical treatments, so be sure to follow label instructions regarding follow-up treatments. Chemicals used to treat humans for lice are regulated by the Food and Drug Administration (FDA) as drugs and are not pesticides registered by the Environmental Protection Agency (EPA).

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
  • Safeway Maximum Strength Lice Treatment Shampoo
    Active ingredient: pyrethrum extract, piperonyl butoxide  |  EPA reg no: N/A
  • RID Lice Killing Shampoo
    Active ingredient: pyrethrum extract, piperonyl butoxide  |  EPA reg no: N/A
  • RiteAid Pyrinyl Lice Shampoo
    Active ingredient: pyrethrum extract, piperonyl butoxide  |  EPA reg no: N/A
  • Equate Maximum Strength Lice Killing Shampoo
    Active ingredient: pyrethrum extract, piperonyl butoxide  |  EPA reg no: N/A
  • This list may not include all products registered for this use.
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Caption: Pubic louse (crabs, crab lice)
Photo by: Ken Grey