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Head Lice

The back of a penny, with a louse egg, nymph, and adult around it. The egg is very small, smaller than the letter 'u' on the penny. The nymph is slightly bigger. The adult is about as long as the building is tall on the back of the penny..
Lice are much smaller than a penny.

The District laboratory works with local public schools to provide training and guidance on preventing, identifying, and managing head lice.

Head lice are tiny parasites that can infest the head and neck area and attach their eggs to the base of the hair shaft. Head lice do not cause disease, but they can itch. Children scratching their scalps can open the skin and cause bacterial infection.

Head Lice Transmission

Head lice can be passed from person to person. Usually this occurs during direct head-to-head contact, such as children playing or reading together, sharing a bed during slumber parties, or playing sports that involve direct contact. Less often, head lice can be transmitted by sharing desks, chairs, or couches, or by sharing bedding, combs and brushes, hats, or clothing.

You cannot get head lice without direct contact or sharing items.

Head lice do not fly or jump and do not travel through the air or through food or drink.

Inspecting for Head Lice

A long light brown line (the hair) has a oval-shaped item attached to it (the louse egg).
A magnified louse nit attached to a single strand of hair.

Head lice often cause itching and scratching of the scalp, but not everyone may react to them. If a child has head lice, all family members and close friends should be checked for lice.

If you believe your child has head lice, you will need to check their scalp. Use a bright light, such as a flashlight or direct sunlight so you can see clearly, and check the hair against the scalp for adult lice and nits (eggs). While adult lice are about the size of a sesame seed, you may need a magnifying glass or reading glasses to see the young lice or nits, which are only a little wider than a human hair. They range in color from almost clear to black. The adults may crawl quickly.

Debris and dandruff can be easily removed, nits cannot. Nits look like white or clear ovals glued tightly to the hair shaft. They will be located within 1/2 inch of the scalp; nits further than 1/2 inch from the scalp have already hatched. In early infections, you may only see nits.

Treating Head Lice Infestations

Head lice are perfectly evolved to infest humans and even the best personal hygiene cannot prevent head lice infestation. They grab tightly to the hair shaft; you cannot shampoo them away.

Lice shampoo can be purchased over-the-counter from most drugstores, or may be obtained by prescription from your doctor. These products must ALWAYS be used exactly as directed by the label or a medical professional. If you skip treatments, or split a box of shampoo between multiple family members, the treatment will not work.

NEVER use other insecticides, household products or products meant for animals in place of registered head lice shampoos. These products have not been tested for safety when used in this way, and may be harmful to the person being treated.

How to treat for lice:

  1. Always follow the instructions on the packaging. Lice shampoo is intended to kill adult lice; it cannot kill the lice nits (eggs).
  2. After shampooing and before the hair dries, comb and part it into sections. Use the lice comb to examine small sections of hair for nits or remaining adult lice, and remove them with your fingernails, the comb, or by cutting the strand of hair with scissors. This process is very important to prevent re-infestation.
  3. Use soapy water and rinse any live lice or nits you find down the sink.
  4. Disinfect all brushes and combs (either by placing them in the dishwasher or scrubbing them with hot soap and water) and place all towels directly into the laundry and wash on hot cycle. If clothing or bedding cannot be washed on hot (look at the garment tag to see the recommended wash instructions), seal it in a plastic bag and let it sit for 2 weeks.
  5. Repeat the above until the lice shampoo has been used up, following instructions on the packaging. Do not stop treatment early. Do not split lice treatments between multiple family members.

Treating the Household

You should examine every family member for lice and treat all of them at the same time. If a family member is not infested, do not treat them, but continue to monitor them for evidence of infestation.

After treatment, launder all bedding where affected family members sleep. Lice cannot survive without a human host, so items that cannot be laundered, like stuffed animals, can be sealed in a plastic bag for two weeks to allow the lice to die. Vacuum all floors and clean upholstered furniture.

You do not need to use household insecticides to treat head lice infestations. Head lice cannot survive more than a few days if they are not on a person’s head, and nits will not hatch unless attached to a hair. You only need to sterilize and clean items that the person used prior to when treatment began. Combs, hairbrushes, and hair ornaments used by a person with head lice should be disinfected to remove any lice or nits.

How to Check for and Treat Head Lice



More Resources

US EPA’s Head Lice Control page

CDC’s Head Lice Treatment FAQ

Head lice information from California Department of Public Health

Head Lice Treatment Information from FDAHead Lice Fact Sheet from SMCMVCD




Page last reviewed: September 24, 2021

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