Pediculosis (Head Lice Infestation)

What is head lice infestation?

The head louse (Pediculus humanus capitis) is one of three types of lice that can infest people. These insects are about the size of a sesame seed (2–3 mm long) and live in human hair where they feed on tiny amounts of human blood. Head lice are hard to see because they are very small, avoid light, and move fast. It is easier to see the eggs (called nits), which attach to the base of the hair, close to the scalp. The eggs may look like dandruff on the scalp. Head lice live only on humans—they do not live on pets.

Who gets head lice infestation?

Anyone can get head lice. In the United States, infestation with head lice is common among children attending childcare and elementary school and their household members and caretakers. According to CDC, about 6–12 million infestations occur every year among children 3–11 years old. Head lice can also appear in group settings, such as sports teams and camps.

How is head lice infestation spread?

Head lice are usually spread by direct contact with the hair of a person infested with head lice. Head lice move by crawling; they cannot hop or fly. The most common way to get head lice is by head-to-head contact with a person who already has head lice. Although less common, head lice may spread by contact with shared objects like combs, brushes, hats, or other personal items. Head lice can be spread as long as lice or eggs remain alive on the person with head lice or in their clothing. Head lice can live on a person’s head for about 30 days and need human blood to survive. They usually do not survive for more than two days away from the human body.

What are the symptoms of head lice infestation?

Head lice can cause a tickling feeling on the scalp or feeling that something is moving under the hair. Head lice can also cause itching. Sometimes there are sores on the head caused by scratching. The sores can become infected. People with lice may also have difficulty sleeping.

How soon after exposure do symptoms appear?

Eggs usually hatch 8–9 days after being laid. Lice mature into adults about 7 days later.

How is head lice infestation diagnosed?

Head lice infestation is diagnosed by finding a live, crawling louse on the scalp or hair of a person. A fine-tooth comb and magnifying glass may help you find lice. If you do not see crawling lice, look for nits attached firmly within ¼ inch of the base of hair shafts. Nits can also be found on hair behind the ears or near the back of the neck. Nits attached more than ¼ inch from the base of the hair shaft are almost always hatched or dead. Head lice infestation is commonly misdiagnosed because nits can look like other hair particles (for example, dandruff, hair spray droplets, and dirt particles).

What is the treatment for head lice infestation?

Persons diagnosed with head lice infestation should be treated with a medicine that is effective against lice (called a pediculicide). Treatment should be considered for anyone sharing a bed with a person with lice. All household members and other close contacts should be examined for infestation. If a household member or close contact is found to be infested, they should be treated on the same day. Detailed guidelines for head lice treatment can be found at the CDC head lice treatment page.

Four critical steps should be followed to control an infestation of head lice:

1. Use an effective head louse treatment. Doctors can recommend a medicated shampoo, cream, or lotion to kill head lice. These can be over-the-counter or prescription medications. Make sure to follow the instructions contained in the box or printed on the label. If your medication kills lice but does not kill eggs, treat again about a week after the first treatment.
2. Use nit combs or a fine-tooth comb to remove nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective.
3. Remove lice and nits from the household by vacuuming, storing, washing, or freezing objects suspected of being infested. All clothing, bed linens, and other items used by a person infested with lice during the two days before treatment should be washed using hot water and high heat drying cycle. Items that are not machine-washable should be dry cleaned or sealed in a plastic bag for two weeks. This gives enough time for any eggs to hatch and the lice to die. Vacuum the floor and furniture, particularly where the infested person sat or laid.
4. After each treatment, check hair and remove nits and lice every 2–3 days for the next 2–3 weeks.

If no dead lice are found after 8–12 hours of treatment and lice seem as active as before, then the medicine might not be working. Speak with your healthcare provider to see if a different medicine is needed. If your healthcare provider recommends a different product, follow the treatment instructions contained in the box or printed on the label.

Do not try to suffocate head lice with olive oil, mayonnaise, butter, margarine, or any similar food-grade product. Do not use motor or machine oils, or kerosene, as these materials can be harmful. Pet shampoo should not be used to treat a lice infestation. Fumigant sprays or fogs should not be used because these can be toxic if inhaled or absorbed through the skin.

How can head lice infestation be prevented?

Head lice can be prevented by avoiding head-to-head contact and not sharing personal items, such as clothing, combs, brushes, hats, scarves, barrettes, helmets, or towels.

To prevent re-infestation and spread of head lice, everyone in the household should be checked. Everyone with head lice should be treated on the same day. Children should not be excluded or sent home early from school or childcare because of head lice. “No-nit” policies should be discouraged.

How can I get more information about head lice?

• If you have concerns about head lice, contact your healthcare provider.
• Call your local health department. You can find your local health department at vdh.virginia.gov/health-department-locator/
• Visit the CDC's page on head lice at cdc.gov/parasites/lice/head/ for more information.