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BackFact Sheet
Treating Head Lice

Update on Head Lice in Schools:
Do ‘No-Nit’ Policies Work?
 May 2001

A recent Centers for Disease Control and Prevention/Georgia Department of Human Resources, Division of Public Health study investigated the probability that schoolchildren found with nits alone will become infested with lice.

According to an article published in the May 7, 2001 issue of Pediatrics, more than 1,700 Atlanta-area schoolchildren were examined for head lice. Ninety-one were found with nits alone or lice. Of the 63 children with nits only, 50 completed the study. Of the 50 children with nits alone, only 9 or 18% became infested with lice during the 2-week follow-up. “This is good evidence that most nits do not develop into lice,” says Allen Hightower, statistician for the study. “There is some evidence that nits found within 1/4 inch of the scalp will develop into lice, but even in these cases, two-thirds did not.” In the study, seven of 22 children with five or more nits found within 1/4 inch of the scalp developed a lice infestation during the 2-week follow-up. The data suggest that health policy developers consider re-evaluating the usefulness of a "no-nit" policy that excludes children from school just because nits alone are found in the hair.

For More Information

Williams LK, Reacher A, Mac Kenzie WR, Hightower AW, Blake PA. Lice, nits, and school policy. Pediatrics 2001;107:1011-1015.

Communicable Disease Surveillance Center. Working document combs out guidance on head lice. Commun Dis Rep CDR Wkly 1998;8:405.

Pollack RJ, Kiszewski AE, Spielman A. Overdiagnosis and consequent mismanagement of head louse infestations in North America. Pediatr Infect Dis J 2000;19:689-793.

Pray WS. Head lice: perfectly adapted human predators. American Journal of Pharmaceutical Education 1999;63:204-209.

Juranek DD. Pediculus capitis in school children: epidemiologic trends, risk factors, and recommendations for control. In: Orkin M, Malback HL, eds. Cutaneous Infestations and Insect Bites. New York, NY:Marcel Kekker, Inc: 1985;199-211.

I have heard that head lice medications do not work, or that head lice are resistant to
medication. Is this true?

A recent study done by Harvard University did show that SOME, but NOT ALL (or even most) head lice are resistant to common prescription and over-the-counter medications (OTC). There is
no information on how widespread resistance may be in the United States. Resistance (medication not working) is more likely in people who have been treated many times for head lice. There are many reasons why medications may seem not to work. Below are some of those reasons: 

  1. Misdiagnosis of a head lice infestation. A person has head lice if they have crawling bugs on their head or many lice eggs (also called nits) within a quarter inch (approximately the width of your pinky finger) of the scalp. Nits found on the hair shaft further than 1/4 inch from the scalp have already hatched out. Treatment is not recommended for people who only have nits further than one-quarter inch away from the scalp.
  2. Not following treatment instructions fully. See instructions below for how to treat a head lice infestation. Using medication alone is not likely to cure a head lice infestation. 
  3. Medication not working at all (resistance). If head lice medication does not kill any crawling bugs, then resistance is likely. If the medication kills some of the bugs, then resistance to medication is probably not the reason for treatment failure (see item #2 and #4).
  4. Medication kills crawling bugs, but is not able to penetrate the nits. It is very difficult for head lice medication to penetrate the nit shell. Medication may effectively kill crawling bugs, but may not treat the nits. This is why follow-up treatment is recommended. See instructions below for a detailed summary.
  5. New infection. You can get infested more than once with head lice. Teach family members how to prevent re-infection. 

How can I treat a head lice infestation?

By treating the infested person, any other infested family members, and by cleaning clothing and bedding. 

Step 1: Treat the infested person/any infested family members

Requires using an OTC or prescription medication. Follow these treatment steps:

  1. Before applying treatment, remove all clothing from the waist up.
  2. Apply lice medicine, also called pediculicide (peh-DICK-you-luh-side), according to label instructions. If your child has extra long hair, you may need to use a second bottle.

    WARNING: Do not use a creme rinse or combination shampoo/conditioner before using lice medicine. Do not re-wash hair for 1-2 days after treatment.
  3. Have the infested person put on clean clothing after treatment.
  4. If some live lice are still found 8-12 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.
  5. If no dead lice are found 8-12 hours after treatment and lice seem as active as before, the medicine may not be working. See your health care provider for a different medication and follow their treatment instructions.
  6. A nit comb should be used to remove nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective. Finer-toothed nit combs, available through Wal-Med* and the National Pediculosis Association*, may also be helpful.
  7. After treatment, check hair every 2-3 days and use a nit comb to remove any nits or lice you see. 
  8. Retreat in 7-10 days. 
  9. Check all treated persons for 2-3 weeks after you think that all lice and nits are gone. 

Step 2: Treat the household

  1. To kill lice and nits, machine wash all washable clothing and bed linens that the infested person touched during the 2 days before treatment. Use the hot water cycle (130o F) to wash clothes. Dry laundry using the hot cycle for at least 20 minutes
  2. Dry clean clothing that is not washable, (coats, hats, scarves, etc.) OR 
  3. Store all clothing, stuffed animals, comforters, etc., that cannot be washed or dry cleaned into a plastic bag and seal for 2 weeks.
  4. Soak combs and brushes for 1 hour in rubbing alcohol, Lysol*, or wash with soap and hot (130o F) water. 
  5. Vacuum the floor and furniture. Do not use fumigant sprays; they can be toxic if inhaled.


My child has head lice. I don't. Should I treat myself to prevent being infested?

No, although anyone living with an infested person can get head lice. Have another person check the back and sides of your head for lice and nits. Check family members for lice and nits every
2-3 days. Treat only if crawling lice or nits are found within a 1/4 inch of the scalp.

Is there a product I can use to prevent getting head lice? 

No.

Should my pets be treated for head lice?

No. Head lice do not live on pets.

My child is under 2 years old and has been diagnosed with head lice. Can I treat him or her with prescription or OTC drugs?

No. For children under 2 years old, remove crawling bugs and nits by hand. If the problem persists, consult your pediatrician.

What OTC medications are available to treat
head lice?

Many head lice medications are available at your local drug store. Each OTC product contains one of the following active ingredients.

  1. Pyrethrins (pie-WREATH-rins): often combined with piperonyl butoxide (pie-PER-a-nil beu-TOX-side): 
    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 7- 10 days to kill any newly hatched lice. Sometimes the treatment does not work.
  2. Permethrin (per-meth-rin):
    Brand name product: 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 necessary in 7-10 days to kill any newly hatched lice. Sometimes the treatment does not work.

    Note: If OTC permethrin (1%) does not effectively kill crawling bugs, prescription- strength (5%) permethrin will not be any more effective. If lice are resistant to 1%, they
    will also be resistant to 5% permethrin.



What are the prescription drugs used to treat head lice? 

Malathion (Ovide *): Malathion has just been reapproved for the treatment of head lice infestations. When used as directed, malathion is very effective in treating lice and nits. Few side-effects have been reported. Malathion may sting if applied to open sores on the scalp caused by scratching. Therefore, do not use if excessive scratching has caused a large number of open sores on the head.

Lindane (Kwell*): Lindane is one of the most common treatments used to treat head lice. When used as directed, the drug is usually safe. Overuse, misuse, or accidentally swallowing of
Lindane can be toxic to the brain and nervous system. Lindane should not be used if excessive scratching has caused open sores on the head. 

Which head lice medicine is best for me?

If you aren't sure, ask your pharmacist or health care provider. When using medicine, always follow the instructions.

When treating head lice

  1. Do not use extra amounts of the lice medication unless instructed. Drugs are insecticides and can be dangerous when misused or overused. 
  2. Do not treat the infested person more than 3 times with the same medication if it does not seem to work. See your health care provider for alternative medication.
  3. Do not mix head lice medications.


Should household sprays be used to kill adult lice?

No. Spraying the house is NOT recommended. Fumigants and room sprays can be toxic if inhaled.

Should I have a pest control company spray my house?

No. Vacuuming floors and furniture is enough to treat the household.

*Use of trade names is for identification purposes only and does not imply endorsement by the Public Health Service or by the U.S. Department of Health and Human Services.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

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This page last reviewed May 2001

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