What are head lice?

Also called Pediculul 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.

Who is at risk for getting head lice?

Anyone who comes in close contact with someone who already has head lice, contaminated clothing, and other belongings. Preschool and elementary-age children 3-10, and their families are infested most often. Girls and women get head lice more often than boys and men. In the United States, African-Americans rarely get head lice.

What do head lice look like?

There are three forms of head lice: the nit, the nymph, and the adult.

Nit: Nits are head lice eggs. They are hard to see and are often confused for dandruff or hair spray droplets. Nits are found firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about 1 week to hatch.

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 grayish-white. In persons with dark hair, the adult louse will look darker. Females lay nits; they are usually larger than males. 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.

What are the signs and symptoms of head lice infestation?

• Tickling feeling of something moving in the hair.
• Itching, caused by the 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?

• By contact with an already infested person.
• By wearing infested clothing such as hats, scarves, coats, sports uniforms, or hair ribbons.
• By using infested combs, brushes, or towels.
• By lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person.

How is head lice infestation diagnosed?

By looking closely through the hair and scalp for nits, nymphs, or adults. If you are not sure if a person has head lice, the diagnosis should be made by a health care provider, school nurse or a professional from the local health department or agricultural extension service.

There are many reasons why medications for head lice don’t work.

Here are some of those reasons:

• Misdiagnosis of head lice infestation.
• Not following treatment instructions fully.
• Medication not working at all (resistance).
• Medication kills crawling bugs, but is not able to penetrate the nits.
• New infection.

Treat the infested person/any infested family members:

Requires using an OTC or prescription medication. Follow these treatment steps:

• Before applying treatment, remove all clothing from the waist up.
• Apply lice medicine according to label instructions. If your child has extra long hair you may need to use an extra bottle.

WARNING: Do not use a crème rinse or combination shampoo/conditioner before using lice medication. Do not rewash hair foe 1-2 days after treatment.

• Have the infested person put on clean clothing after treatment.
• If some 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 sometimes takes linger to kill the lice.
• If no dead lice are found 8-12 hours after treatment and lice seem as active as before, the medicine may not be working. See your health care professional.
• A nit comb should be used to remove nits and lice from the hair shaft. Many hair combs made for cats and dogs are also effective.
• After treatment, check hair every 2-3 days and use a nit comb to remove any nits or lice you see.
• Retreat in 7-10 days.
• Check all treated persons for 2-3 week after you think that all lice and nits are gone.

Treat the household:

• To kill lice and nits, machine wash all washable clothing and bed linens that the infested person touched during the 2 days before treatment. Use the hot water cycle (130° F) to wash clothes. Dry laundry using the hot cycle for at least 20 minutes.
• 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 and seal for 2 weeks.
• Soak combs and brushed for 1 hour in rubbing alcohol, Lysol®, or wash with soap and hot (130°) water.
• Vacuum the floor and furniture. Do not use fumigant sprays, they can be toxic if inhaled.

Sources: CDC (Center for Disease Control and Prevention) and HeadLice.org (The National Pediculosis Association )

Updated: January 4, 2005