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Head Lice 

What are head lice?

Also called Pediculus humanus capitis (peh-DICK-you-lus HUE-man-us CAP-ih-TUS), head lice are parasitic insects found on the heads of people. Having head lice is very common. However, there are no reliable data on how many people get head lice in the United States each year.

Causes of head lice

Anyone who comes in 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 elementary-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.

Types of head lice

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

Egg/Nit: Nits are head lice eggs. They are very small, about the size of a knot in thread, hard to see, and are often confused for dandruff or hair spray 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 1 week to hatch. Eggs that are likely to hatch are usually located within 1/4 inch of the scalp.  

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 7 days after hatching. To live, the nymph must feed on blood.

Adult: The adult louse is about the size of a sesame seed, has six legs, and is tan to greyish-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.  


Signs and symptoms of head lice infestation

  • Tickling feeling of something moving in the hair.
  • Itching, caused by an allergic reaction to the bites.
  • Irritability.
  • Sores on the head caused by scratching. These sores can sometimes become infected.

How did my child get head lice?

Contact with an already infested person 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 commonly,

  • Wearing clothing, such as hats, scarves, coats, sports uniforms, or hair ribbons, recently worn by an infested person.
  • Using infested combs, brushes, or towels.
  • Lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person.

Head lice infestation diagnosis


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. 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. 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, the diagnosis should be made by your health care provider, school nurse, or a professional from the local health department or agricultural extension service.

Treatment of head lice infestation

The most important step in treating a head lice infestation is to treat the person and other family members with head lice with medication to kill the lice. Wash clothing and bedding worn or used by the infested person in the 2-day period just before treatment is started.

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

  1. Before applying treatment, remove all clothing from the waist up. Apply lice medicine, also called pediculicide (peh-DICK-you-luh-side), according to label instructions. If your child has extra long hair (longer than shoulder length), you may need to use 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 crème rinse or combination shampoo/conditioner before using lice medicine.
  2. Do not re-wash hair for 1-2 days after treatment.Have the infested person put on clean clothing after treatment.
  3. 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.
  4. 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.
  5. Nit (head lice egg) combs, often found in lice medicine packages, should be used to comb nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective.
  6. 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.
  7. If using OTC pediculicide, retreat in 7-10 days. If using the prescription drug malathion, retreat in 7-10 days ONLY if crawling bugs are found. Click here for instructions on how to use malathion to treat head lice.

Household treatment for head lice

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 help avoid 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 2 days before treatment. Use the hot water (130°F) cycle. Dry laundry using high heat for at least 20 minutes.
  2. Dry clean clothing that is not washable, (coats, hats, scarves, etc.).or store all clothing, stuffed animals, comforters, etc., that cannot be washed or dry cleaned into a plastic bag; seal for 2 weeks.
  3. Soak combs and brushes for 1 hour in rubbing alcohol, Lysol*, or wash with soap and hot (130°F) 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.

Prevention of head lice 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 a head lice outbreak in a community, school, or camp, you can teach children to avoid playtime and other activities that are likely to spread lice.

  • Avoid head-to-head contact common during play at school and at home (sports activities, on a playground, slumber parties, at camp).
  • Do not share clothing, such as hats, scarves, coats, sports uniforms, or hair ribbons.
  • Do not share infested combs, brushes, or towels.
  • Do not lie on beds, couches, pillows, carpets, or stuffed animals that have recently been in contact with an infested person.
 
   
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