Head Lice

What are head lice?

Lice are tiny insects that live on humans and feed on blood. When a large number of lice live and multiply on a person, it is called an infestation.

• Head lice are usually found in hair, most often on the back of the neck and behind the ears. Head lice are common in preschool and elementary school-age children. Adults can get them too, especially adults who live with children. 

What causes a lice infestation?

Lice spread easily from one person to another through close contact or through shared clothing or personal items (such as hats or hairbrushes). A louse cannot jump or fly.

What are the symptoms?

Head lice may not cause any symptoms at first. Itching on the scalp may start weeks or even months after lice have started to spread. Scratching can make the skin raw. The raw skin may ooze clear fluid or crust over, and it may get infected.

Frequent scratching can cause a skin infection. In the most severe cases of head lice, hair may fall out, and the skin may get darker in the areas infested with lice.

How is a lice infestation diagnosed?

A doctor can usually tell if you have lice by looking closely for live lice or eggs in your hair. The doctor may also comb through your hair with a fine-toothed comb to help detect lice. He or she may look at the lice or eggs under a microscope.

How is it treated?

Lice won’t go away on their own. Be sure to do all you can to treat lice and to prevent the spread of lice.

The most common treatment is an over-the-counter or prescription cream, lotion, or shampoo. You put it on the skin or scalp to kill the lice and eggs. In some cases, you may need treatment a second time to make sure that all the eggs are dead. If two or more treatments don't work, your doctor may prescribe a different medicine.

It’s also important to wash clothing and bedding in hot water to help get rid of lice.

Some people have an allergic reaction to lice bites that causes itching for 7 to 10 days after the lice and eggs have been killed. Steroid creams or calamine lotion can relieve the itching. If you have severe itching, you can try antihistamine pills. But don't give antihistamines to your child unless you've checked with the doctor first.

Cleaning Lice From Combs, Clothing, and Other Items

Lice can spread from human to object to human, but it's more common for lice to spread by human to human contact. Lice don't live longer than 2 days when they are not on a human.

Removing lice from personal items, clothing, and furniture is one way to help prevent lice from spreading to other household members. And it may help prevent a person who has been treated for lice from becoming reinfested.

• To rid hair brushes, combs, barrettes, and other hair ornaments of lice, soak them in hot water [greater than 54.5°C (130°F)] for 10 minutes, soak them in isopropyl alcohol, or wash them with a shampoo that is used to treat head lice.
• Wash clothes, bedding, and cloth toys in hot water [greater than 54.5°C (130°F)] in an automatic washing machine or place them in a hot dryer for at least 10 minutes. Dry-cleaning or storing clothing in a plastic bag for 2 weeks will also destroy head and pubic lice. (Storage of clothing is recommended for body lice, although storage is needed for up to 30 days because body lice can survive that long.)
• Vacuum carpets, upholstery, and mattresses.
• You do not need to fumigate the house with insecticide sprays. This will not help treat or control a lice problem and may unnecessarily expose family members to toxic fumes. 

Removing Nits From Hair

Lice eggs stick to the hair and can be hard to remove. It is possible that if some eggs survive treatment and are not removed from the hair, they may persist or spread to someone else.

You can try wet combing to remove eggs and lice:

• Wet your hair and add conditioner, vinegar, or olive oil. Then comb your hair with a fine-toothed comb. Comb for at least 15 minutes (until you find no more lice.) Repeat this process every few days. Stop 2 weeks after the last session in which you found an adult louse.
• If you are using medicine to kill lice, you can use a fine-toothed comb after you've rinsed the medicine from your hair. The combs are often packaged with over-the-counter lice shampoos.

Wet combing is an option for infants who can't use lice medicines. Also, some people use a comb to remove eggs after using lice medicine on the hair or just because they don't like the look of lice and eggs in the hair.

Last Revised: January 28, 2011

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Donald Sproule, MD, CM, CCFP, FCFP - Family Medicine & Susan C. Kim, MD - Pediatrics

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