Healthy Schools - Head Lice

Head Lice

Head lice information for schools

According to the Centers for Disease Control and Prevention (CDC), students diagnosed with live head lice do not need to be sent home early from school; they can go home at the end of the day, be treated, and return to class after appropriate treatment has begun. Nits may persist after treatment, but successful treatment should kill crawling lice.

Head lice can be a nuisance but they have not been shown to spread disease. Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.

Both the American Academy of Pediatrics (AAP) and the National Association of School Nurses (NASN) advocate that “no-nit” policies should be discontinued. “No-nit” policies that require a child to be free of nits before they can return to schools should be discontinued for the following reasons:

  • Many nits are more than ¼ inch from the scalp. Such nits are usually not viable and very unlikely to hatch to become crawling lice, or may in fact be empty shells, also known as ‘casings’.
  • Nits are cemented to hair shafts and are very unlikely to be transferred successfully to other people.
  • The burden of unnecessary absenteeism to the students, families and communities far outweighs the risks associated with head lice. Students miss learning opportunities when burdened by over-cautious school policies.
  • Misdiagnosis of nits is very common during nit checks conducted by nonmedical personnel.

What are head lice?

Head lice are parasitic insects that can be found most commonly on the scalp, particularly around and behind the ears and near the neckline at the back of the head. They are less commonly found on the eyebrows or eyelashes of people. Head lice feed on human blood several times a day. They live close to the human scalp. Head lice are not known to spread disease.

Who is at risk for getting head lice?

Head lice are found worldwide. In the United States, head lice are most common among pre-school children attending child care, elementary schoolchildren, and the household members of infested children. An estimated 6 million to 12 million infestations occur each year in the United States among children 3 to 11 years of age. In the United States, infestation with head lice is much less common among African-Americans than among persons of other races.

Head lice move by crawling; they cannot hop or fly. Head lice are spread by direct contact with the hair of an infested person. Anyone who comes in head-to-head contact with someone who already has head lice is at greatest risk. Spread by contact with clothing (such as hats, scarves or coats) or other personal items (such as combs, brushes or towels) used by an infested person is uncommon. Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice. Dogs, cats, and other pets do not have a role in the spread of head lice.

What do head lice look like?

Head lice have three forms: the egg (also called a nit), the nymph, and adult. 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 and are very small. Nits are often confused with dandruff, scabs, hair spray droplets or dirt particles. Head lice nits usually take 8 to 9 days to hatch. A nymph is an immature louse that hatches from the egg. A nymph looks like an adult head louse but is much smaller. A nymph must feed on blood to live. Nymphs mature into adults after 9 to 12 days from hatching. An adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white in color. They too must feed on blood to live. An adult can live about 30 days on a person’s head but will die within 1 or 2 days if it falls off. Adult female head lice are usually larger than males.

What are the signs and symptoms of head lice infestation?

  • Tickling feeling of something moving in the hair.
  • Itching caused by an allergic reaction to the bites of lice.
  • Irritability and difficulty sleeping as head lice are more active in the dark.
  • Sores on the head caused by scratching. These sores can sometimes become infected from bacteria on the person’s skin.

Do head lice spread disease?

Head lice should not be considered as a medical or public health hazard. Head lice are not known to spread disease. Head lice can cause a tickling feeling or a sensation of something moving in the hair. Head lice can be an annoyance because their presence may cause itching and loss of sleep. Sometimes the itching can lead to excessive scratching that can sometimes increase the chance of a secondary skin infection.

Diagnosis of head lice infestation:

Misdiagnosis of head lice infestation is common. The diagnosis of head lice infestation is best made by finding a live nymph or adult louse on the scalp or hair of a person.

Because adult and nymph lice are very small, move quickly, and avoid light, they may be difficult to find. Use of a fine-toothed louse comb may help to identify live lice.

If crawling lice are not seen, finding nits attached firmly within ¼ inch of the base of hair shafts suggests, but does not confirm, the person is infested. Nits frequently are seen on hair behind the ears and near the back of the neck. Nits that are attached more than ¼ inch from the base of the hair shaft are almost always hatched or dead. Head lice and nits can be visible with the naked eye, although use of a magnifying lens may be necessary to find crawling lice or to identify a developing nymph inside a nit. Nits are often confused with other particles found in hair such as dandruff, hair spray droplets and dirt.

If no nymphs or adults are seen, and the only nits found are more than ¼ inch from the scalp, then the infestation is probably old and no longer active — and does not need to be treated.

General guidelines for treatment of head lice:

There are both prescription and over-the –counter treatments for head lice infestations. Treatment for head lice is recommended for persons diagnosed with an active infestation. All household members and other close contacts should be checked; those with evidence of an active infestation should be treated. Some experts believe preventative treatment is prudent for persons who share the same bed with actively-infested individuals. All infested persons (household members and close contacts) and their bedmates should be treated at the same time.

Some medicines that kill lice also kill nits. For medicines that state they are not effective at killing nits or state they do not, routine retreatment is recommended. For those that are able to kill nits, retreatment is recommended only if live (crawling) lice are still present several days after treatment (you must read the recommendation for each medication used). To be most effective, retreatment should occur after all nits have hatched but before new nits are produced.

When treating head lice, supplemental measures can be combined with recommended medicine; however, these additional measures generally are not required to eliminate a head lice infestation. For example, hats, scarves, pillow cases, bedding, clothing and towels worn or used by the infested person in the 2-day period just before treatment is started can be machine washed and dried using the hot water and hot air cycles. This is because lice and nits are killed by exposure for 5 minutes to temperatures greater than 128.3°F or 53.5°C. Items that cannot be laundered may be dry-cleaned or sealed in a plastic bag for two weeks. Items such as hats, grooming aids and towels that come in contact with the hair of an infested person should not be shared. Vacuuming furniture and floors can remove an infested person’s hairs that might have viable nits attached.

Always use your health care provider or pharmacist’s recommendations when treating someone with head lice.

Tennessee Head Lice Manual 2022

Tennessee Head Lice Manual

View or download this comprehensive guide to identify, treat, and prevent head lice infestations for use by health departments, healthcare providers, childcare and school facilities, and parents.


Government partners

Centers for Disease Control and Prevention
Head lice information for schools
Head lice webpage

US Food and Drug Administration
Treating and preventing head lice

Additional resources

National Association of School Nurses
Position Statement for Head Lice Management in the School Setting

American Academy of Pediatrics
AAP updates treatments for head lice

Harvard College
Head lice advice for childcare flowchart

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