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Head Lice

Head lice are parasitic insects found on the heads of people. Having head lice is very common.

Who is at risk for getting head lice?

Anyone who comes into close contact (especially head-to-head contact) with someone who already has head lice is at greatest risk. Occasionally, head lice may be acquired from contact with clothing (such as hats, scarves, coats) or other personal items (such as brushes or towels) that belong to an infested person.

Preschool and school-age children 3-11 and their families are infested most often. Girls get head lice more often than boys, women more than men. In the United States, African-Americans rarely get head lice.

Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.

What do head lice look like?

There are three forms of lice: the egg (also called a nit), the nymph, and the adult.

Headlice Compared to a Penny
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Head LIce Egg

Head Lice Egg/nit

Nits are head lice eggs. They are very small, about the size of a poppy seed, hard to see, and often mistaken for dandruff or hairspray droplets. Nits are laid by the adult female at the base of the hair shaft nearest the scalp. They are firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about a week to hatch. Eggs that are likely to hatch are usually located within 1/4 inch of the scalp.   

headlice nymph

Head Lice Nymph

The nit hatches into a baby louse called a nymph. It looks like an adult head louse but is smaller. Nymphs mature into adults about a week after hatching.

To live, the nymph must feed on blood from the scalp.

Adult head louse

Adult Head Lice

The adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white. In persons with dark hair, the adult louse will look darker. Females, which are usually larger than the males, lay eggs.

Adult lice can live up to 30 days on a person's head. To live, adult lice need to feed on blood. If the louse falls off a person, it dies within 2 days. 

Where are head lice most commonly found?

They are most commonly found on the scalp, behind the ears and near the neckline at the back of the neck. Head lice hold on to hair with hook-like claws found at the end of each of their six legs. Head lice are rarely found on the body, eyelashes, or eyebrows.

What are the signs and symptoms of head lice infestation?

How did my child get head lice?

Contact with a person who is already infested is the most common way to get head lice. Head-to-head contact is common during play at school and at home (sports activities, on a playground, slumber parties, at camp). Less common ways include:

If you think your child might have come into contact with someone infected with head lice, keep an eye out for nits appearing in his or her hair. An infected person may be asymptomatic for up to 6 weeks of exposure. 

How is head lice infestation diagnosed?

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An infestation is diagnosed by looking closely through the hair and scalp for nits, nymphs, or adults. Finding a nymph or adult may be difficult; there are usually few of them and they can move quickly from searching fingers. It’s helpful to wet the hair (lice move more quickly through dry hair) and use bright lighting and a magnifying glass.

If crawling lice are not seen, finding nits within a 1/4 inch of the scalp confirms that a person is infested and should be treated. When searching for nits, pay close attention to the top of the neck and around the ears. If you only find nits more than 1/4 inch from the scalp (and don't see a nymph or adult louse), the infestation is probably an old one and does not need to be treated.

If you are not sure if a person has head lice, a diagnosis should be made by your health care provider, school nurse, or a professional from the local health department or agricultural extension service.

How can I treat a head lice infestation?

The most important step in treating an infestation is to treat all affected family members with head lice medication to kill the lice. Wash clothing and bedding worn or used by any infested person in the two-day period before treatment is started.

Treat the infested person: This requires an over-the-counter (OTC) or prescription medication. Follow these steps:

  1. Before applying treatment, remove all clothing from the waist up.
  2. Apply lice medicine, also called pediculicide, according to label instructions. If your child has extra long hair (longer than shoulder length), you may need a second bottle. Pay special attention to instructions on the bottle regarding how long the medication should be left on and whether rinsing the hair is recommended after treatment.WARNING: Do not use a cream rinse or combination shampoo/conditioner before using lice medicine. Do not re-wash hair for 1-2 days after treatment.
  3. Have the infested person put on clean clothing after treatment.
  4. If a few live lice are still found 8-12 hours after treatment, but are moving more slowly than before, do not retreat. Comb dead and remaining live lice out of the hair. The medicine may take longer to kill lice.
  5. If, after 8-12 hours of treatment, no dead lice are found and lice seem as active as before, the medicine may not be working. See your health care provider for a different medication; follow treatment directions.
  6. Use a nit (head lice egg) comb, often found in lice medicine packages, to comb nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective.
  7. After treatment, check hair and comb with a nit comb to remove nits and lice every 2-3 days. Continue to check for 2-3 weeks until you are sure all lice and nits are gone.
  8. If using OTC pediculicides, re-treat in 7-10 days. If using the prescription drug malathion, re-treat in 7-10 days ONLY if crawling bugs are found.

Treat the household: Head lice do not survive long if they fall off a person and cannot feed. You don't need to spend a lot of time or money on housecleaning activities. Follow these steps to prevent re-infestation by lice that have recently fallen off the hair or crawled onto clothing or furniture.

  1. To kill lice and nits, machine wash all washable clothing and bed linens that the infested person wore or used during the two days before treatment. Use the hot water cycle. Dry laundry using high heat.
  2. Dry-clean clothing that is not washable. Or store all clothing, stuffed animals, and comforters that cannot be washed or dry cleaned into a plastic bag; seal for two weeks.
  3. Soak combs and brushes for an hour in rubbing alcohol, spray them with Lysol, or wash with soap and hot water.
  4. Vacuum the floor and furniture. The risk of getting re-infested from a louse that has fallen onto a carpet or sofa is very small. Don't spend a lot of time on this. Just vacuum the places where the infested person usually sits or lays. Do not use fumigant sprays; they can be toxic if inhaled or absorbed through the skin.

Prevent reinfestation: Lice are most commonly spread directly by head-to-head contact and much less frequently by lice that have crawled onto clothing or belongings. As a short-term measure to control an outbreak in a community, school, or camp, direct children to avoid playtime and other activities that are likely to spread lice.

My child has head lice. I don't. Should I treat myself to prevent being infested?

No, although anyone living with an infested person can get head lice. Check household members for lice and nits every 2-3 days. Treat only if crawling lice or nits (eggs) within a 1/4 inch of the scalp are found.

I have heard that head lice medications don't work, or that head lice are resistant to medication. Is this true?

Like germs that are resistant to antibiotics, some lice also develop resistance to the medicine used to kill them. Resistance tends to be scattered. It may be present in one neighborhood, but not another. However, there are many reasons why medications may seem not to work.

1.Misdiagnosis of a head lice infestation. A diagnosis can be made if a person has crawling bugs on the head or many lice eggs within 1/4 inch (about the width of your little finger) of the scalp. Nits found on the hair shaft further than 1/4 inch from the scalp have already hatched. Treatment is not recommended for people who only have nits further than 1/4 inch away from the scalp.

2.Not following treatment instructions fully. Common problems include:

3.Medication not working at all (resistance). If head lice medication does not kill any crawling bugs within 24 hours, then resistance is likely. If the medication kills some of the bugs or the bugs are twitching 24 hours after treatment then resistance to medication is probably not occurring.

4.Medication kills crawling bugs, but is not able to penetrate the eggs. It is very difficult for head lice medication to penetrate the nit shell. Medication may effectively kill crawling bugs, but may not treat the nits. This is why follow-up treatment is recommended.

5.New infection. You can get infested more than once with head lice. Children often get re-infested from a playmate. If your child is infested, discuss it with parents of the children your child plays with. Treating all infested children at the same time will help prevent reinfestation.

Should my pets be treated for head lice?

No. Head lice do not live on pets.

My child is under 2 years old and has been diagnosed with head lice. Can I treat him or her with prescription or OTC drugs?

For children under 2 years old, remove crawling bugs and nits using a nit comb. If this does not work, ask your child's health care provider for treatment recommendations. The safety of head lice medications has not been tested in children 2 years of age and under.

What OTC medications are available to treat head lice?

Many head lice medications are available at your local drug store. Each OTC product contains one of the following active ingredients.

What prescription drugs are used to treat head lice?

Which head lice medicine is best for me?

If you aren’t sure, ask your doctor or health care provider. When using the medicine, always follow instructions on the package insert unless the physician directs otherwise.

When treating head lice:

Should household sprays be used to kill adult lice?

No. Spraying the house is NOT recommended. Fumigants and room sprays can be toxic if inhaled or absorbed through the skin.

Should I have a pest control company spray my house?

No. Vacuuming floors and furniture is enough to treat the household.

Do head lice spread other diseases?

No. The head lice do not transmit illnesses to people.


Reference: CDC