Disease Fact Sheet Series:

What is pediculosis?
Pediculosis is an infestation of lice. Body lice infestations occur primarily on clothing, especially along the seams of inner surfaces and the adjacent area of the skin. Pubic/crab lice infest hairy parts of the body including the groin, eyebrows, eyelashes and facial hair. Both body lice and pubic/crab lice feed on human blood and can cause severe local itching.

Who gets pediculosis?
Anyone can become infested with body lice or pubic/crab lice, regardless of age, sex, race, or standards of personal hygiene. Body lice infestation are usually found in people living in crowded, unsanitary conditions where clothing is infrequently changed or laundered. Pubic/crab lice infestations are mainly found among sexually active individuals.

How are body lice and pubic/crab lice spread?
Body lice are spread from person-to-person through close direct contact with a lice infested area of a person or through sharing of unlaundered clothes or bedding that had recent contact with an infested person. While other means are possible, pubic/crab lice are usually spread through sexual contact. Since nits (louse eggs) must be laid by adult lice and need warm temperatures to hatch, the chances of nits being spread from person-to-person are minimal.

Do animals spread body lice or pubic/crab lice?
No. Lice from animals do not infest humans.

What are the symptoms of pediculosis?
The first indication of an infestation is usually itching around the area of the body where the lice feed. Itching in the groin area should lead to an examination for louse nits (eggs) in that area. Severe scratching may result in secondary bacterial infection in these areas. Pubic/crab lice do not spread disease. Body lice are capable of spreading certain diseases like epidemic typhus, relapsing fever, and trench fever, none of which are common in Wisconsin or the United States.

How soon do symptoms appear?
It may take two to three weeks for a person to notice the intense itching associated with pediculosis.

How long is a person able to spread body lice or pubic/crab lice?
Lice can be spread as long as they remain alive on the infested person or their clothing.

What can be done to prevent the spread of pediculosis?
Avoid physical contact with infested individuals and their belongings, especially clothing and bedding. Close contacts and playmates of infested persons should be examined. Clothing and linen that have been in contact with an infested individual within 2 days of being diagnosed should be washed in hot water (>130o F) or machine dried at the hottest setting for 20 minutes. Other articles may be dry cleaned or sealed in plastic bags for at least 10 days to destroy lice and eggs. In addition, parents should perform lice checks of children when excessive itching is noticed. Fogging with insecticides or spraying the environment with lice-killing chemicals is not recommended.

How long do body lice and pubic/crab lice live away from the body?
Unattached to the body and without a blood meal, body lice survive for approximately 10 days and pubic/crab lice survive approximately 24 hours.

What is the treatment for pediculosis?
There are several medicated shampoos commonly used to treat pubic/crab lice. Shampoos or creme rinses containing 1% permethrin have the fastest killing time against adult lice and the highest nit-killing capability. Permethrin has a residual effect that will continue to kill nits for several days after the first application. While one application should be sufficient to kill lice and nits, some experts suggest a second treatment one week after the first. Although resistance to permethrin has been reported from other countries, no resistance has been reported in the United States.

Shampoos which contain pyrethrin kill lice quickly but do not leave a residual that will continue to kill nits, resulting in a less effective treatment. Two applications of the types of shampoos 7-10 days apart are recommended to kill nits.

Shampoos containing malathion and lindane are available by prescription only. Lindane has the slowest killing time for pubic/crab lice (up to several hours) and lowest nit killing capability. Lindane is not recommended for young children, or pregnant or nursing women, and should only be used if other approved therapies did not work or can not be tolerated. Misuse or overuse of lindane may be toxic. There are widespread reports from countries other than the United States of lice being resistant to lindane.

For infestation of pubic/crab lice on the eyelashes, petroleum ointment applied 3-4 times daily for 8-10 days is effective.

Because body lice spend most of the time on clothing except for short periods of time on skin when feeding, persons with body lice should not be treated with lice-killing medications. To control body lice, clothing and bedding that had contact with an infested person should be washed and dried at the hottest temperature possible to kill the lice and nits.

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Last Revised: June 21, 2011