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Head lice

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Illustrations

Head lice
Head lice
Lice, head - nits in the hair with close-up
Lice, head - nits in the hair with close-up
Head louse emerging from egg
Head louse emerging from egg
Head louse, male
Head louse, male
Head louse - female
Head louse - female
Head louse infestation - scalp
Head louse infestation - scalp

Alternative names    Return to top

Lice - head; Nits; Pediculosis capitis - head lice

Definition    Return to top

Head lice are tiny insects that live on the scalp. They can be spread by close contact with other people.

Causes, incidence, and risk factors    Return to top

There are three common types of lice: head lice, body lice, and pubic lice (also called crabs). Head lice infect the scalp hair and are easiest to see at the nape of the neck and over the ears. Tiny eggs can be seen on the hair, appearing much like flakes of dandruff, but stuck firmly to the hair shaft instead of flaking off the scalp.

Lice can also live on clothing, carpets, or bedding.

Head lice are spread easily and cause intense itching, but they do not lead to a serious medical problem. Lice are more common in close, overcrowded living conditions. Lice spread readily among school children.

Having lice is NOT an indicator of poor hygiene or low social status.

Symptoms    Return to top

Signs and tests    Return to top

Lice can be seen and identified by looking closely. Using disposable gloves, inspect the head of anyone who might have been exposed to lice under a bright light. Full sun or the brightest lights in your home during daylight hours work well. A magnifying glass can also help.

Part the hair all the way down to the scalp in very small sections, looking both for moving lice and eggs (nits). Inspect the entire head this way. Look closely around the nape of the neck and ears, the most common locations for eggs. Treatment is recommended if even one egg is found.

The infestation may be confined to the scalp or may include the surface of the body (body lice), including the groin area (pubic lice).

Treatment    Return to top

Lotions and shampoos containing permethrin are usually effective. They are available over-the-counter. If these do not work, other products are available by prescription. The medications used for lice are insecticides. Therefore, they should be used exactly as directed and no more frequently than recommended.

Certain products loosen the bond between the egg sack (nit) and hair shaft so that eggs can be easily removed. Remove the eggs with a nit comb. Removing eggs may prevent reinfection if the medication fails to kill all of them.

Treat children and adults with lice promptly and thoroughly. Wash all clothes and bed linens. This also helps prevent head lice from spreading to others.

Expectations (prognosis)    Return to top

Lice are usually killed with proper treatment. However, reinfestation is possible, especially if the source of the infestation is not corrected (for example, a classroom with many infected children).

Complications    Return to top

Some people will develop a secondary skin infection from scratching.

Calling your health care provider    Return to top

First, apply home treatment. Call your health-care provider if symptoms continue after home treatment, or if you develop an irritation from the medicine.

Prevention    Return to top

Update Date: 12/2/2003

Updated by: Jacqueline A. Hart, M.D., Department of Internal Medicine, Newton-Wellesley Hospital, Boston, Ma., and Senior Medical Editor, A.D.A.M., Inc. Previously reviewed by Philip L. Graham III, M.D., Department of Pediatrics, Children's Hospital of New York, Columiba Universit, New York, NY. Review provided by VeriMed Healthcare Network (1/22/2002).

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The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.