Head lice

Definition

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

These lice only live in hair and occasionally eyebrows and eyelashes.

See also:

Body lice 

Pubic lice

Causes, incidence, and risk factors

Head lice infect hair on the head. They are easiest to see on the neck and over the ears. Tiny eggs on the hair look like flakes of dandruff  . However, innstead of flaking off the scalp, they stay put.

Head lice can survive on clothing, carpets, or bedding for up to 10 days. Their eggs can live for more than 2 weeks.

Head lice spread easily. You can get head lice when you come in close contact with an infested person or touch their clothing or bedding. Head lice are more common in close, overcrowded living conditions. Lice spread easily among school children.

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

Head lice causes intense itching, but does not lead to a serious medical problem. Unlike body lice, head lice never carry or spread diseases.

Symptoms

• Intense itching of the scalp
• Small, red bumps on the scalp, neck, and shoulders
• Bumps may become crusty and ooze
• Tiny white specks (eggs, or nits) on the bottom of each hair that are hard to get off

Lice on scalp and clothing may be difficult to see, unless the infestation is heavy. If you see something moving, it's called a louse.

Signs and tests

To see head lice, you need to look closely. Use disposable gloves and look at the person's head under a bright lead. 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). Look at the entire head this way. Look closely around the top of the neck and ears, the most common locations for eggs.

Treatment is recommended if even one egg is found.

Treatment

Lotions and shampoos containing permethrin are usually effective. They are available over-the-counter. If these do not work, a doctor can give you a prescription for medicine that contain insecticides. Such medicine should be used exactly as directed.

Certain products make the eggs (nits) easier to remove. Some dishwashing detergents can help dissolve the "glue" that makes the nits stick to the hair shaft.

• You can remove the eggs with a nit comb. Before doing this, rub olive oil in the hair or run the metal comb through beeswax. This helps make them easier to remove.
• Metal combs with very fine teeth are stronger and more effective than plastic nit combs. These metal combs are easier to find in pet stores or on the Internet than in pharmacies.
• Removing eggs may prevent the lice from returning if the medication fails to kill every one of them.
• Treat children and adults with lice promptly and thoroughly.
• Wash all clothes and bed linens in hot water with detergent. This also helps prevent head lice from spreading to others during the short period when head lice can survive off the human body.

Treatment can cause significant side effects in children younger than 6 months old, the elderly, and anyone weighing less than 110 lbs (50 kg), especially when the treatment is used repeatedly in a short period of time.

Expectations (prognosis)

Lice are usually killed with proper treatment. However, lice may come back, especially if the source is not corrected. For example, a classroom with many infected children can cause kids to repeatedly get lice.

When one case is detected in a family or a school or child-care center, every child at that location should be examined for head lice. This can help prevent further spreading.

Complications

Some people will develop a secondary skin infection from scratching. Antihistamines can help relieve the itching. 

Calling your health care provider

Call your health-care provider if symptoms continue after home treatment, or if you develop areas of red, tender skin, which could mean a possible infection.

Prevention

Never share hair brushes, combs, hair pieces, hats, bedding, towels, or clothing with someone who has head lice.

If your child has lice, be sure to 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.

Some schools may have policies to make sure the environment is clear of lice. Sometimes, the insects or their eggs get into areas such as carpets. Frequent cleaning of carpets and all other surfaces in child-care centers prevents spread of all types of infections, including head lice.

References

Long SS, Pickering LK, Prober, CG, eds. Principles and Practice of Pediatric Infectious Diseases. 2nd Ed. New York, NY: Churchill Livingstone, 2003.

Mandell GL, Bennett JE, Dolin R, eds. Principles of Infectious Diseases. 5^th Ed. New York, NY: Churchill Livingstone, 2000:2972-2973.

Goetz CG, Pappert EJ. Textbook of Clinical Neurology. 2^nd Ed. Philadelphia, PA: Saunders; 2003.

Illustrations

Head lice

Nit on human hair

Lice, head - nits in the hair with close-up

Head louse emerging from egg

Head louse, male

Head louse - female

Head louse infestation - scalp

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