Pediculosis capitis - head lice

Alternative names
Lice - head; Nits; Head lice

Definition
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

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

     
  • Intense itching of the scalp.  
  • Small, red bumps on the scalp, neck, and shoulders. Bumps may become crusty and ooze.  
  • Lice on scalp and clothing. These may be difficult to see, unless the infestation is heavy)  
  • Eggs (nits) on the hair shaft - tiny white specks firmly attached to the base of the hair shaft.

Signs and tests

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

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)

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

Some people will develop a secondary skin infection from scratching.

Calling your health care provider

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

     
  • Check policies at schools, daycares, preschools, and nurseries. Many do not allow infected children to be at school until the lice have been completely treated. Sometimes, however, the insects get into carpets or other areas at the school. It is helpful if the school has policies to ensure the environment is cleared of lice.  
  • DO NOT share hair brushes, combs, hair pieces, hats, bedding, towels, or clothing with someone who has lice.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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