Head lice are tiny parasitic insects (Pediculus humanus capitis) that live on the scalp and can be spread by close contact with other people.

Alternative Names

Lice - head; Nits; Pediculosis - head lice; Pediculosis capitis

Causes, incidence, and risk factors

There are three common types of lice: head lice, body lice , and pubic lice . Head lice infect the scalp hair and are easiest to see at the nape of the neck and over the ears. Small eggs can be seen on the hair shafts. They appear much like flakes of dandruff , but are stuck firmly to the hair shaft instead of flaking off of the scalp. Head lice do not cause a serious medical problem and do not spread other diseases (as body lice do), but they are spread very easily. Risk factors include close, overcrowded living conditions. Lice also spread readily among school children. It is important to note that having lice is not an indicator of poor hygiene or low socioeconomic status.

Signs and tests

Examination is sufficient to determine the presence of lice. Inspect the head of anyone who might have been exposed to lice using 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 insects and nits. Inspect the entire head this way. Look closely around the nape of the neck and ears, the most common locations for nits. Treatment is recommended if even one nit 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

Over-the-counter and prescription lotions and shampoos (pediculicides) are reasonably effective. Resistance to these pediculicides is growing, making it increasingly difficult to clear up infections. Disinfect bed clothing, combs, brushes, hats and other personal hygiene items (typically wash in hot, soapy water) to prevent reinfestation. Do this the same time the affected person is treated. Examples of medications used include:

Lindane (available by prescription only)

Nix (available over-the-counter)

Rid (available over-the-counter)

Remember that these medications are (in reality) insecticides, and should be used exactly as directed and no more frequently than recommended in the package insert. New products are available that loosen the bond between the nit (egg sack) and the hair shaft so that the nits can be easily removed (only to be used with one of the pediculicides). Remove nits with a nit comb. Removal of all nits may prevent reinfection if the medication fails to kill all of the eggs.

Expectations (prognosis)

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

Complications

Some people will develop a secondary skin infection from scratching.

Calling your health care provider

Apply home treatment and call your health-care provider if symptoms persist after treatment, or if you develop irritation from the medicine.

Prevention

Effective treatment of infected people and bed clothing will prevent head lice from spreading to others. Most schools have a policy of sending infected children home until the head lice are treated. However, this is often not effective in preventing the continued spread of the infestation.