Nits are the eggs of lice, laid by the females at the base of the scalp. Nits are very small, egg-shaped, and are often confused for dandruff or hair product particles. They typically appear to be white or pale yellow, but sometimes they can be the same color as the infected person’s hair. The eggs are located on strands of hair about 1/4 inch from a person’s scalp. If they are farther than 1/4 inch from a person’s scalp, they may be casings or have already hatched.


A nymph is an immature louse that hatches from the nit. It looks like an adult louse but is much smaller. It can only survive if it feeds on blood. They mature in about 9-12 days.


An adult louse is about the size of a sesame seed, and is typically grayish-white in color but may also be the color of the person’s hair. Adults have six legs with hooks on the end to adhere to the scalp. To live, they must feed on blood. Females are usually larger than males, and they can lay up to six eggs a day. Adults can live for about 30 days on the scalp. They can not live longer than 1-2 days without blood.

General Information

What are head lice?

The head louse is a parasitic insect that can be found on the scalp, eyebrows, or eyelashes on humans. They feed on the blood near the scalp. They are not known to spread disease.

Who can get head lice?

Anybody can get head lice, although it is most common amongst younger children, who typically pick up lice from daycare, school, or preschool. Personal hygiene and cleanliness of the home is not related to whether one can get head lice or not.

How does head lice spread?

Head lice are spread by crawling from direct contact. They cannot jump or fly. Typically, head lice can only spread through direct contact with an infected person’s hair. It is rare for lice to spread through clothing or personal hygiene items such as towels and brushes.

Where are head lice most commonly found?

Head lice are typically found behind the ears and at the nape of the neck near the scalp. However, they can be found anywhere on the scalp. Occasionally, a person may get lice on their eyebrows or eyelashes, but this is rare.

What are the symptoms of head lice?

  • Tickling feeling in the hair (like something moving)
  • Itching of the scalp
  • Difficulty sleeping (head lice are most active in the dark)
  • Sores on the scalp from scratching; this can occasionally lead to infections

How is a lice infestation diagnosed?

The best way to diagnose head lice is to find a live adult or nymph louse on the scalp. However, nymph and adult lice are difficult to find, because they typically avoid light. Sometimes, a comb and magnifying glass may be needed to identify the infestation. If it is not possible to find crawling lice, it can be diagnosed if an egg is found 1/4 inch near the scalp on strands of hair. This can be difficult to determine, because eggs oftentimes look like dandruff or hair product particles. If no crawling lice are found, and hatched eggs are found more than 1/4 inch past the scalp, it is likely that the infestation has moved on and does not have to be treated. However, if you can not determine whether someone has lice, they should be taken to a healthcare professional or health department to confirm diagnoses.

How is head lice treated?

See Treatment below.

How can I prevent getting or spreading head lice?

  • Avoid head-to-head contact with infested persons
  • Do not share clothing, especially hats and scarves
  • Do not share personal hygiene items such as brushes and towels
  • Do not lie on beds, carpets, pillows, etc. that an infected person has recently used
  • Wash infected clothing in hot water (above 130*F) or get them dry cleaned
  • Vacuum carpets where infected persons have been playing or lying down
  • Do not use fumigant sprays or fogs as they do not help control lice


How can I treat head lice?

Over-the-counter medications approved by the FDA are available at most drug stores. Follow the directions according to the box. If the lice are not gone after a full treatment, see your doctor who can prescribe a prescription treatment. Follow the treatment according to your doctor’s recommendation. If the lice are not gone after a full treatment, call your healthcare provider.

All head lice treatments should be used according to directions. Do not use more than directed, and do not try more than one treatment at one time.

Before treating children, contact their healthcare provider for a treatment that will be effective for their age and weight.

What should I do if the treatment is not working?

If your treatment is not working, it can be for a variety of reasons including:

  1. Misdiagnoses
  2. Applying the treatment to hair that has been washed with conditioner, which can protect the hair from the treatment.
  3. Not following the instructions for treatment carefully.
  4. Resistance to the treatment used.
  5. Reinfestation

If your treatment is not working for you, contact your healthcare provider who can provide you with an effective treatment.

What are the side effects of using head lice treatments?

Treatments are generally safe and usually do not have any side effects. Occasionally, a person may experience side effects such as:

  • Itching
  • Burning
  • Inflammation of the scalp

Is it necessary to remove all of the nits?

No. The treatments are usually spaced 9 days apart, which helps eliminate all live and potentially live lice on the scalp. However, removal of nits can be used for aesthetic purposes or to reduce the chance of a second infestation.

For more information on head lice, visit  http://www.cdc.gov/parasites/lice/head/index.html.