Head Lice (Pediculosis)
What are head lice?
Head lice are tiny insects that feed on blood from the human scalp and lay their eggs on hair. Head lice are very common, particularly in children. There is no connection between head lice and the length of someone's hair or the cleanliness of their hair, body, or home or school environment.
The medical name for head lice is pediculosis humanus capitis.
How do people get head lice?
Head-to-head contact with a person who already has head lice is the most common way to get head lice. Head-to-head contact is common at home and school, in sports, on the playground, and at slumber parties and camp.
It's very uncommon, but possible, to get head lice from clothing or belongings containing lice or nits that have crawled or fallen from a person with head lice. Examples include:
- Recently worn or used hats, scarves, coats, sports uniforms or items such as hair ribbons, barrettes, combs, brushes, towels, and stuffed animals
- Beds, sofas, pillows or carpet. (The risk of getting head lice from a louse or nit that has fallen onto carpet or furniture is very small, however.)
Head lice cannot hop or jump, and they do not have wings, so they cannot fly.
You cannot catch head lice from dogs, cats, and other pets – head lice cannot survive on them.
Do head lice carry disease?
Head lice are not known to transmit any disease and therefore are not considered a health hazard. However, people with head lice sometimes develop bacterial infections from scratching the skin or scalp.
What are the symptoms?
The most common sign of head lice is itching, but most people do not develop itching until after head lice have been present for several weeks. Other possible symptoms are a tickling feeling of something moving in the hair and sores on the head caused by scratching. Irritability and difficulty sleeping may also be signs, since head lice are most active in the dark.
What do head lice look like?
Head lice are most often found on the scalp behind the ears and near the neckline at the back of the neck. Occasionally, they are also found on a person's eyebrows and eyelashes.
There are three stages in the lifecycle of head lice, and each stage looks different.
- Nits – Each day, a female louse lays 3-6 eggs, called nits. Nits are oval-shaped and very small – about the size of a knot in thread. Firmly attached to the hair shaft, nits often appear yellow or white, although they can sometime appear to be the same color as a person's hair. Nits are hard to see, and people sometimes mistake dandruff, scabs and hair spray droplets for nits. Nits are also hard to remove.
- Nymph – Within 7-10 days, a nit hatches into a baby louse called a nymph. A nymph has six legs and is tan to grayish-white in color. Nymphs feed on blood and mature into adults in about 9-12 days.
- Adult – The adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white in color. It may look darker in people with dark hair. Adult lice feed on blood from the scalp, and each adult can live about 30 days on a person's head. An adult louse will die within one or two days if it falls off the person.
Who is at risk for head lice?
In the United States, head lice are most commonly found among preschool children attending child care centers, elementary school children, and household members of children with head lice.
- Girls get head lice more often than boys, and women more than men.
- While it is possible for African-Americans to get head lice, they rarely do. This may be because the claws of the head louse found most frequently in the United States are better adapted for grasping the shape and width of the hair shaft of other races.
How do you treat (get rid of) head lice?
Many head lice medications are available over-the-counter. To treat for head lice, follow these steps:
- Before applying treatment, remove all clothing from the waist up.
- Apply lice medicine according to the label instructions. Do not use hair conditioner or combination shampoo/conditioner before using lice medicine. Do not re-wash hair for 1-2 days after treatment.
- Put on clean clothing after treatment.
- If you find some lice still alive 8-12 hours after treatment, but the lice are moving more slowly than before, the medicine may just be taking longer to kill the lice. Comb dead lice and any remaining live lice out of the hair using a nit comb, which you can buy at your local drugstore. (A flea comb made for cats and dogs may also work.)
- If you do not find any dead lice 8-12 hours after treatment and the live lice seem as active as before, the medicine may not be working. Contact your doctor for a different medication and follow their treatment instructions.
- After treatment, check the hair every 2-3 days and continue to use a nit comb to remove any nits or lice you see.
- Use the lice medicine again in 7-10 days according to product instructions.
- Check the hair for 2-3 weeks after you think that all lice and nits are gone.
Take these steps to help prevent the spread of head lice to other members of your household:
- Use the hot water cycle for at least 20 minutes to machine wash all washable clothing and bed linens touched by the person with head lice in the two days before treatment. Dry the laundry using the hot cycle for at least 20 minutes.
- Dry clean clothing that is not washable (coats, hats, scarves, etc.) and place clothing, stuffed animals, comforters or other items that cannot be dry cleaned or washed into plastic bags. Seal the bags for two weeks.
- Soak combs and brushes for 1 hour in rubbing alcohol, or wash with soap and hot water.
- Vacuum the floor and furniture.
Are there any side effects from using chemical treatments for head lice?
According to the U.S. Centers for Disease Control and Prevention (CDC), chemical treatments for head lice are generally safe and effective when used correctly. Some treatments may cause an itching or a mild burning sensation caused by inflammation of the skin on the scalp. Most products used to treat head lice are pesticides that can be absorbed through the skin. Therefore, all medicines used for the treatment of lice should be used with care and only as directed.
What can be done to stop the spread of head lice?
The best way to prevent the spread of head lice is to limit contact with others until the person with head lice has been treated as outlined.
What are schools supposed to do when head lice is found on a child's head?
School-age children who are not medically fragile should be sent home at the end of the school day if head lice are discovered. The child may return to school with a parent note after they have been treated once with a school-approved lice-removal product. Your child's school may recommend options for head lice treatment.