Head lice-Head lice - Diagnosis & treatment - Mayo Clinic (2024)


According to the American Academy of Pediatrics guidelines, the gold standard for diagnosing head lice is to identify a live nymph or adult louse.

The guidelines recommend examining wet hair lubricated with hair conditioner or another product. Your child's health care provider will carefully comb your child's hair with a fine-toothed comb (nit comb) from the scalp to the end of the hair. If no live louse is found, the provider will likely repeat the entire exam at a second appointment.

Identifying nits

Your health care provider will also look for nits in your child's hair. To find nits, your child's provider may use a specialized light called a Wood's light, which causes nits to appear bluish. But the identification of nits does not necessarily confirm the diagnosis of live lice.

A live nit needs to be near the scalp to survive. Nits found more than about 1/4 inch (6 millimeters) from the scalp are likely dead or empty. Suspect nits can be examined under a microscope to determine if they're living.

If the provider doesn't find any live nits, they're probably left from a previous case of head lice and don't need to be treated.


Your health care provider will likely recommend a medication available without a prescription that kills lice and some of the nits. These medications may not kill recently laid eggs. Therefore, an appropriately timed second treatment is usually necessary to kill nymphs after they hatch but before they become adult lice.

Some studies suggest that re-treating 7 to 9 days after the first treatment is the ideal time for a second treatment, but other re-treatment schedules exist. Ask your health care provider for written instructions for a recommended treatment schedule.

Nonprescription products

Medications available without a prescription include:

  • Permethrin (Nix). Permethrin is a synthetic version of pyrethrin, which is a chemical compound extracted from the chrysanthemum flower. Permethrin is toxic to lice.

    Before using permethrin, wash your child's hair with shampoo but not conditioner. Rinsing the hair with white vinegar before washing may help dissolve the glue that holds the nits to the hair shafts. Leave the medication in the hair for the amount of time indicated in the directions on the package. Then rinse your child's hair over a sink with warm water.

    Permethrin doesn't kill nits, and treatment needs to be repeated 9 to 10 days after first application. Side effects may include redness and itching of the scalp.

  • Ivermectin (Sklice). Ivermectin is toxic to lice. The lotion is approved for use in adults and children age 6 months or older. It can be applied once to dry hair and then rinsed with water after 10 minutes.

Prescription medications

In some regions, lice have developed resistance to nonprescription medications. Nonprescription treatment also may fail because of incorrect use, such as not repeating the treatment at an appropriate time.

If the correct use of a nonprescription treatment has failed, your health care provider may recommend a prescription treatment. These include:

  • Spinosad (Natroba). Spinosad is approved for adults and children age 6 months and older. It can be applied to dry hair and rinsed with warm water after 10 minutes. It kills lice and nits and usually doesn't need repeated treatment.
  • Malathion. Malathion is approved for adults and children age 2 or older. The lotion is applied, left to dry naturally and rinsed out after 8 to 12 hours. The drug has a high alcohol content, so it can't be used with a hair dryer or near an open flame. Malathion can be reapplied 7 to 9 days after the first treatment if necessary.
  • Ivermectin (Stromectol). In addition to the nonprescription lotion, ivermectin is available by prescription as a tablet to be taken by mouth. It can be given to children weighing more than 33 pounds if other topical treatments don't rid the scalp of head lice.

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See Also
Head Lice

Self care

If you prefer not to use a medication for treating head lice, you may consider a home treatment. However, there's little to no clinical evidence that home treatments are effective.


Combing wet hair with a fine-toothed nit comb may remove lice and some nits. Studies show that wet-combing results vary.

Start by wetting the hair and lubricating it with hair conditioner or olive oil. Comb the entire head from the scalp to the end of the hair at least twice during a session. The process typically should be repeated every 3 to 4 days for several weeks — at least two weeks after no more lice are found.

Essential oils

Small clinical studies have suggested that some natural plant oils may kill lice by depriving them of air, but effectiveness is uncertain. These products include:

  • Tea tree oil
  • Anise oil
  • Ylang-ylang oil

Essential oils aren't required to meet safety, efficacy and manufacturing standards used for drugs approved by the Food and Drug Administration (FDA), and can sometimes cause allergic reactions.

Smothering agents

A number of household products are used to treat head lice. These products are thought to deprive the lice of air when generous amounts are applied to the hair, covered with a shower cap and left on overnight. Products used for this purpose include:

  • Mayonnaise
  • Olive oil
  • Margarine or butter
  • Petroleum jelly

However, it's unclear if these treatments are effective.


Another option is a machine that uses one application of hot air to kill head lice and their eggs through dehydration. The machine requires special training and is currently available only at professional lice treatment centers.

The machine uses air that is cooler than most hair dryers and at a much higher flow rate to kill the lice by drying them out. Don't use a regular hair dryer to accomplish this result as it's too hot and could burn the scalp.

Dangerous products to avoid

Flammable products, such as kerosene or gasoline, should never be used to kill lice or to remove nits.

Household cleaning

Lice usually don't live past one day without feeding from a human scalp. And eggs can't survive without the temperature near the scalp. Therefore, the chance of lice surviving on household items is small.

As a precaution, you may clean items that the affected person has used in the previous two days. Cleaning recommendations include the following:

  • Wash items in hot water. Wash bedding, stuffed animals and clothing in hot, soapy water — at least 130 degrees Fahrenheit (54.4 degrees Celsius) — and dry at high heat.
  • Clean hair care items. Clean combs, brushes and hair accessories by soaking them in hot, soapy water for 5 to 10 minutes.
  • Seal items in plastic bags. Seal items that can't be washed in plastic bags for two weeks.
  • Vacuum. Give the floor and upholstered furniture a good vacuuming.

Preparing for your appointment

See your family's health care provider or pediatrician if you suspect that your child has head lice. The provider will examine your child's scalp and look for a live nymph or adult louse to determine if he or she has head lice. The provider can carefully inspect your child's hair. If necessary, the provider can examine suspect items under a microscope before confirming that head lice are present.

Head lice-Head lice - Diagnosis & treatment - Mayo Clinic (2024)


What does a severe lice infestation look like? ›

A long-term body lice infestation may lead to thickening and discoloration of the skin, particularly around the waist, groin, and upper thighs, causing a condition called “vagabond's disease”. Intense scratching can cause sores, which may lead to bacterial or fungal infections.

What happens if you have head lice for too long? ›

If you have untreated head lice, a bacterial infection requiring antibiotics can result. In rare, severe cases , head lice and nits can lead to iron deficiency anemia due to blood loss. An unchecked infestation can also spread to your eyebrows and eyelashes, although this is rare.

What is the diagnosis for lice? ›

A health care provider may diagnose head lice after finding a live young or adult louse in the person's hair or on the scalp, or after seeing one or more nits on hair shafts found within 1/4 inch (6 millimeters) of the scalp.

Is one lice treatment enough? ›

Dual treatment—and combing— are often required

Permethrin is pediculicidal (ie, it kills only live lice); it is not ovicidal (ie, it does not kill nits at every stage). Thus, a second application is usually needed 7 to 10 days after the first to ensure complete eradication.

How long does it take to get rid of a bad lice infestation? ›

It takes several treatments to completely remove lice and nits from your hair. It could take up to three weeks to get rid of all lice and nits. Make sure all members of your household check and receive treatment for head lice if one member of your household has head lice, as lice easily spread from person to person.

What's the worst lice can do? ›

Their bites can make the scalp itchy and irritated, and scratching can lead to infection. Head lice are annoying, but they're not dangerous and they don't spread disease. They're not a sign of poor hygiene — head lice need blood and they don't care whether it's from someone who's clean or dirty.

How long can lice live on bedding? ›

As with furniture and carpets, adult lice typically live for around 2 days on pillows and sheets without human contact. Nits will not hatch and will die within a week. People should machine wash any pillows or sheets someone with lice has used in hot water of more than 130°F (54.4°C) .

Can I sleep in my bed if I have lice? ›

Lice are most often spread by head-to-head contact with another person who has lice, such as sleeping in the same bed. Although they do not survive long away from a human host, lice may also be spread by wearing another person's hat or clothing, or by using another person's comb, brush, or bedding.

Is it bad to have lice for years? ›

Left untreated, head lice can lead to secondary infections, which can be serious. Bacterial infections, such as impetigo, can occur when scratched bites become infected; this can have serious consequences if not treated properly.

What kills lice immediately? ›

Washing, soaking, or drying items at a temperature greater than 130°F can kill both head lice and nits. Dry cleaning also kills head lice and nits.

What disease is associated with lice? ›

Due to their blood feeding behaviour, body lice can transmit a great variety of diseases, such as epidemic typhus (caused by Rickettsia prowazekii), louse-borne relapsing fever (caused by Borrelia recurrentis), or trench fever (caused by Bartonella quintana) [3].

Can you self diagnose head lice? ›

Look for lice crawling on the scalp where the hair is parted or on the hair shaft. The lice will be dark in color and the size of a poppyseed. Look for nits near hair follicle about ¼ inch from scalp. Nits (eggs) will be white or yellowish-brown.

Do dead lice fall out of hair? ›

The female louse secretes this glue-like substance when she lays her eggs to protect them until they hatch. The glue hardens upon secretion and does not dissipate when a nit dies. For that reason, dead lice remain cemented onto the hair shaft until you manually or chemically remove them or the hair grows out.

Do nits pop when they are dead? ›

Head lice eggs are small (the size of a pinhead) and oval. A live egg will 'pop' when squashed between fingernails. Dead eggs have crumpled sides and hatched eggs look like tiny boiled eggs with their tops cut off. To optimise treatment remove as many eggs as possible.

What should I do if I find one head lice? ›

Medicated lotions and sprays

These kill head lice in all types of hair, and you can buy them from pharmacies, supermarkets or online. Head lice should die within a day. Some lotions and sprays come with a comb to remove dead lice and eggs. Some treatments need to be repeated after a week to kill any newly hatched lice.

How many head lice is a bad infestation? ›

If you have head lice, you'll usually have up to around 30 lice living on your scalp. But if you have a severe case, there could be up to 1,000 lice. Female head lice lay eggs near your scalp. The eggs are attached to your hair with a glue-like substance.

How bad can a lice infestation get? ›

Body lice bites can cause intense itching, and you may notice small areas of blood and crust on your skin at the site of the bite marks. See your doctor if improved hygiene doesn't remove the infestation, or if you develop a skin infection from scratching the bites.

How many lice are in a typical infestation? ›

Infested children usually carry fewer than 20 mature head lice (more commonly less than 10), each of which, if untreated, live for three to four weeks (5–7). Head lice stay close to the scalp for food, warmth, shelter and moisture (6,7).

How do you get rid of super lice infestation? ›

How to Treat Super Lice. If you have active lice, you should start by using pyrethrin shampoo or other over-the-counter lice treatments. Make sure to carefully comb your hair with a nit comb every night, and wash and dry linens, clothing, hats, and scarves. Repeat the treatment after 7 days.

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