Kirkland Family Medical Center
Head lice are parasitic insects found on the heads of people. Having head lice is very common.
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.
There are three forms of lice: the egg (also called a nit), the nymph, and the adult.
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.
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 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.
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.
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.
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.
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:
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.
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.
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.
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.
No. Head lice do not live on pets.
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.
Many head lice medications are available at your local drug store. Each OTC product contains one of the following active ingredients.
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:
No. Spraying the house is NOT recommended. Fumigants and room sprays can be toxic if inhaled or absorbed through the skin.
No. Vacuuming floors and furniture is enough to treat the household.
No. The head lice do not transmit illnesses to people.