Head Lice: Signs, Symptoms, Diagnosis, Treatment And Prevention

Head Lice: Signs, Symptoms, Diagnosis, Treatment And Prevention


What are head lice?

Also called Pediculus 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; as many as 6-12 million people worldwide get head lice each year. 

Head Lice Signs, Symptoms, Diagnosis, Treatment And Prevention
Head Lice Picture

  • Head lice are parasites that are found on human heads. The word lice is plural for louse.
  • Head lice are spread by personal contact or the sharing of combs, brushes, caps, and other clothing.
  • Head lice are a common problem with preschool and schoolchildren.
  • Head lice cause a tickling feeling of something moving in the hair, itching, and sores on the head.
  • The affected individual, family members also infected, and the home all should be treated.
  • Remember: one head louse + one head louse = two head lice = the beginning of a head-lice infection.
  • Very young children should be evaluated by a health care professional before beginning medications.

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 get head lice more often than boys, women more than men. In the United States, African-Americans rarely get head lice.

Read more: Migraine Headache Causes, Symptoms, Diagnosis, Treatment

Where are head lice most commonly found?


On the scalp behind the ears and near the neckline at the back of the neck. Head lice hold on to hair with hook-like claws found at the end of each of their six legs. Head lice are rarely found on the body, eyelashes, or eyebrows. 

What do head lice look like?


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

Head Lice Signs, Symptoms, Diagnosis, Treatment And Prevention
Head Lice

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 greyish-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.

How did my child get head lice?


  • By contact with an already infested person. Contact is common during play at school and at home (slumber parties, sports activities, at camp, on a playground).
  • 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.

What are the signs and symptoms of head lice infestation?


  • Tickling feeling of something moving in the hair.
  • Itching, caused by the an allergic reaction to the bites.
  • Irritability. 
  • Sores on the head caused by scratching. These sores can sometimes become infected. 

How is head lice infestation diagnosed?


By looking closely through the hair and scalp for nits, nymphs, or adults. Finding a nymph or adult may be difficult; there are usually few of them and they can move quickly from searching fingers. If crawling lice are not seen, finding nits within a 1/4 inch of the scalp confirms that a person is infested and should be treated. If you only find nits more than 1/4 inch from the scalp, the infestation is probably an old one and does not need to be treated. 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. 

What is the treatment for a head lice infestation (pediculosis)?


For effective elimination of head lice, the infested individual, family members that are also infested, and the home must all be treated.

Treatment of the individual and the infected family members


Over-the-counter (OTC) or prescription medications are used to treat the affected people and their families. Follow these treatment steps:

Remove all clothing.

Apply lice medicine, also called pediculicide, according to the label instructions. If your child has extra-long hair, you may need to use a second bottle. WARNING: Do not use a cream rinse or combination shampoo/conditioner before using lice medicine. Do not rewash hair for one to two days after treatment.

Have the infested person put on clean clothing after treatment.

If some live lice are still found eight to 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 longer to kill the lice.

If, eight to 12 hours after treatment, no dead lice are found and lice seem as active as before, the medicine may not be working. See your health care professional for a different medication and follow their treatment instructions.

Nit (head lice egg) combs, often found in lice medicine packages should be used to remove nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective.

After the initial treatment, check, comb, and remove nits and lice from hair every two to three days.

Retreat in seven to 10 days.

Check all treated people for two to three weeks until you are sure all lice and nits are gone.


Treating the house:


Head Lice Signs, Symptoms, Diagnosis, Treatment And Prevention
Head Lice

Treating the whole house is a laborious but important task. Follow these steps:

Machine wash all washable clothing and bed linens that the infested person touched during the two days before treatment (to kill the lice and nits). Use the hot water cycle (130 F; 55 C) 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 it for two weeks.

Soak combs and brushes for one hour in rubbing alcohol, Lysol, or wash with soap and hot (130 F; 55 C) water and then place in bag and leave in freezer for two days.

Vacuum the floor and furniture. Do not use fumigant sprays. (They can be toxic if inhaled.)

What OTC medications are available to treat head lice?


Many head lice medicines are available at your local drugstore. Each OTC product usually contains one of the following active ingredients:

Pyrethrins (often combined with piperonyl butoxide, in brand name products: A-200, Pronto, R&C, RID, Triple X): Pyrethrins are natural extracts from the chrysanthemum flower. Though safe and effective, pyrethrins only kill crawling lice, not unhatched nits. A second treatment is recommended in seven to 10 days to kill any newly hatched lice. Treatment failures are common.

Permethrins (NIX): Permethrins are similar to natural pyrethrins. Permethrins are safe and effective and may continue to kill newly hatched eggs for several days after treatment. A second treatment may be needed in seven to 10 days to kill any newly hatched lice. Treatment failures are common.

Dimethicones (silicone oils, Hedrin, NYDA) coat surfaces and act as a physical barrier asphyxiating the louse and have been shown to be variably effective in studies depending upon the formulation.

Are any home remedies effective at getting rid of head lice?


Occlusion therapy, nit combing, and hair removal have not been proven to be fully effective in completely eradicating head lice.

Home remedies that have been tried include vinegar, mayonnaise, petroleum jelly, olive oil, butter, rubbing alcohol, and prolonged water submersion. These all fail to eliminate infestation, because these therapies do not kill all of the eggs or lice. This is believed due to the specialized way the parasite "breathes."

Hair removal has never been proven to be effective, but since the louse requires a hair shaft to lay its eggs, it should prevent the lice from multiplying. This is not always considered a desirable option for many children.

How can I prevent head lice?


It's not always so easy to prevent head lice 100% of the time since it is a common infestation. Whenever possible, do not share hats or head coverings. Also avoid sharing combs and brushes with other individuals, since it can be transferred this way. If exposed to another individual diagnosed with head lice, continue to check the hair for eggs or adult lice every couple of days, but do not treat unless head lice are discovered.