Head Lice Infestation (Pediculosis)
There are three forms of lice: the egg (also called a nit), the nymph, and the adult.
that easily and safely gets rid of unwanted hair.
Egg/Nit: Nits are head lice eggs. They are very small, about the size of a knot in thread, hard to see, and are often confused for dandruff or hair spray droplets. Nits are laid by the adult female at the base of the hair shaft nearest the scalp. They are firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about 1 week to hatch. Eggs that are likely to hatch are usually located within 1/4 inch of the scalp.
Illustration of egg on a hair shaft (Image credit: CDC)
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.
Nymph form (Photo credit: CDC)
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, which are usually larger than the males, lay eggs. 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. Photo of an adult louse.
Adult louse (Image credit: CDC)
Where are head lice most commonly found?
They are 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.
Photo of adult louse claws. (Photo credit: CDC)
What are the signs and symptoms of head lice infestation?
How did my child get head lice?
Contact with an already infested person is the most common way to get head lice. Head-to-head contact is common during play at school and at home (sports activities, on a playground, slumber parties, at camp).
How is head lice infestation diagnosed?
Picture: Searching for lice in hair. Photo credit: CDC
An infestation is 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 (and don't see a nymph or adult louse), 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 your health care provider, school nurse, or a professional from the local health department or agricultural extension service.
How can I treat a head lice infestation?
The most important step in treating a head lice infestation is to treat the person and other family members with head lice with medication to kill the lice. Wash clothing and bedding worn or used by the infested person in the 2-day period just before treatment is started.
Treat the infested person: Requires using an over-the-counter (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 (longer than shoulder length), you may need to use a second bottle. Pay special attention to instructions on the bottle regarding how long the medication should be left on and whether rinsing the hair is recommended after treatment.
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 a few 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 may take longer to kill lice.
5. If, after 8-12 hours of treatment, no dead lice are found and lice seem as active as before, the medicine may not be working. See your health care provider for a different medication; follow treatment directions.
6. Nit (head lice egg) combs, often found in lice medicine packages, should be used to comb nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective.
7. After treatment, check hair and comb with a nit comb to remove nits and lice every 2-3 days. Continue to check for 2-3 weeks until you are sure all lice and nits are gone.
8. If using OTC pediculicides, retreat in 7-10 days. If using the prescription drug malathion, retreat in 7-10 days ONLY if crawling bugs are found. Click here for instructions on how to use malathion to treat head lice.
Treat the household: Head lice do not survive long if they fall off a person and cannot feed. You don't need to spend a lot of time or money on housecleaning activities. Follow these steps to help avoid re-infestation by lice that have recently fallen off the hair or crawled onto clothing or furniture.
1. To kill lice and nits, machine wash all washable clothing and bed linens that the infested person wore or used during the 2 days before treatment. Use the hot water (130°F) cycle. Dry laundry using high heat for at least 20 minutes.
2. 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; seal for 2 weeks.
3. Soak combs and brushes for 1 hour in rubbing alcohol, Lysol*, or wash with soap and hot (130°F) water.
4. Vacuum the floor and furniture. The risk of getting re-infested from a louse that has fallen onto a carpet or sofa is very small. Don't spend a lot of time on this. Just vacuum the places where the infested person usually sits or lays. Do not use fumigant sprays; they can be toxic if inhaled or absorbed through the skin.
Prevent Reinfestation: Lice are most commonly spread directly by head-to-head contact and much less frequently by lice that have crawled onto clothing or belongings. As a short-term measure to control a head lice outbreak in a community, school, or camp, you can teach children to avoid playtime and other activities that are likely to spread lice.
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. Check household contacts for lice and nits every 2-3 days. Treat only if crawling lice or nits (eggs) within a 1/4 inch of the scalp are found.
I have heard that head lice medications don't work, or that head lice are resistant to medication. Is this true?
Like germs that are resistant to antibiotics, some lice also develop resistance to the medicine used to kill them. Resistance tends to be scattered. It may be present in one neighborhood, but not another. However, there are many reasons why medications may seem not to work.
* Misdiagnosis of a head lice infestation. A diagnosis can be made if a person has crawling bugs on the head or many lice eggs within 1/4 inch (about the width of your little finger) of the scalp. Nits found on the hair shaft further than 1/4 inch from the scalp have already hatched. Treatment is not recommended for people who only have nits further than 1/4 inch away from the scalp.
2. using a creme rinse or conditioner shampoo before applying a pediculicide — this interferes with the medication
3. failure to leave the pediculicide on long enough — follow drug label instructions
4. re-shampooing the hair again immediately after applying the pediculicide — don’t rewash hair for 1-2 days after treatment
5. inadequate amount of medication — extra long hair may require two bottles of pediculide to fully wet the hair
6. not combing. Using medication alone may not be enough to cure a head lice infestation. Combing the hair to remove lice and eggs has been shown to help.
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?
For children under 2 years old, remove crawling bugs and nits using a nit comb. If this does not work, ask your child's health care provider for treatment recommendations. The safety of head lice medications has not been tested in children 2 years of age and under.
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 include 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. Treatment failures are common.
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 lice for several days after treatment. A second treatment may be necessary in 7-10 days to kill any newly hatched lice that may have hatched after residual medication from the first treatment was no longer active. Treatment failures are common.
If you aren’t sure, ask your pharmacist or health care provider. When using the medicine, always follow the instructions on the package insert unless the physician directs otherwise.
When treating head lice
1. Do not use extra amounts of the lice medication unless instructed. These 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 drugs.
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 or absorbed through the skin.
Should I have a pest control company spray my house?
No. Vacuuming floors and furniture is enough to treat the household.
Treating Head Lice Infestation with Malathion
Malathion (Ovide* lotion) was re-approved by the Food and Drug Administration (FDA) as a prescription drug for the treatment of head lice infestation in the United States. Follow the directions below to treat a head lice-infestation.
Step 1: Treat the person infested with head lice:
1. Before applying malathion lotion, remove all clothing from the waist up.
2. Apply malathion according to label directions, to dry hair until the scalp and hair are wet and thoroughly coated. Leave the medication on the hair for 8-12 hours; allow the hair to dry naturally. Have the person put on clean clothing once medication has been applied.
3. (Consider treating just before bedtime. Once malathion has been applied to the hair and scalp, cover any pillow(s) with a towel to keep medication from staining the pillow.)
4. After 8-12 hours, thoroughly wash hair.
5. A nit (head lice egg) comb should be used to remove lice and nits from the hair. Many flea combs made for cats and dogs are also effective.
6. After treatment, check hair for lice and comb hair with a nit comb to remove nits and lice every 2-3 days. Continue checking for 2-3 weeks until you are sure all lice and nits are gone.
7. If crawling bugs are found 7-10 days after treatment, retreat with the same or different louse medication.
Warnings and Precautions:
1. Malathion may cause stinging, especially if the scalp has open sores from scratching.
2. Malathion is flammable. Keep medication out of the eyes and away from heat sources such as hair dryers, electric curlers, cigarettes, or open flames.
3. Pregnant and nursing mothers should only use malathion after consulting their physician.
Step 2: Treat the household:
Head lice do not live long if they fall off a person. You do not need to spend a lot of time or money on house cleaning activities. Follow these steps to help avoid re-infestation by lice that have recently fallen off the hair or crawled onto clothing or furniture.
1. To kill lice and nits, machine wash all washable clothing and bed linens that the infested person has worn or slept on during the 2 days before treatment. Use the hot water (130°F) cycle. Dry laundry using high heat for at least 20 minutes.
2. Dry clean clothing worn 2 days before treatment if it 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 for 2 weeks.
3. Soak combs and brushes for 1 hour in rubbing alcohol, Lysol* , or wash with soap and hot (130°F) water.
4. Vacuum the floor and furniture. Do not use fumigant sprays; they can be toxic if inhaled or absorbed through the skin.
Step 3: Prevent Reinfestation:
Lice are most commonly spread directly by head-to-head contact and indirectly though sharing contaminated clothing or belongings. Teach your child to avoid playtime and other activities that are likely to spread lice.
Are treatment failures with malathion common?
No, however reinfestation is common.
Is a second treatment needed?
Maybe. If crawling lice are still found, a second treatment may be given in 7-9 days. Other family members should be checked for signs of infestation.
Does malathion kill head lice eggs?
No. However, some medication remains on the hair for several days to kill any lice that may hatch after initial treatment.
*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.