Malathion Frequently Asked Questions


What is malathion?

Malathion (Ovide* lotion) is a prescription drug approved by the U.S. Food and Drug Administration (FDA) for the treatment of head lice infestation. The malathion lotion approved in the United States for the treatment of head lice is safe and effective when used as directed. Malathion lotion (Ovide*) is both pediculicidal (kills live lice) and partially ovicidal (kills some lice eggs).

What steps do I follow to treat with malathion?

Step 1: Treat the person(s) infested with head lice:

  1. Always follow your physician’s and pharmacist’s instructions and those contained inside the package or written on the label.
  2. Carefully apply the malathion lotion to dry hair until the scalp and hair are wet and thoroughly coated, especially behind the ears and on the back of the head and neck.
  3. The manufacturer recommends leaving the medication on the hair, uncovered, for 8–12 hours. Allow the hair to dry naturally; do not use an electrical heat source, including a hair dryer or curling iron while the hair is wet. Have the person being treated put on clean clothing once the medication has been applied. Consider treating just before bedtime. Cover any pillow(s) with a towel to keep the medication from staining the pillow.
  4. After 8–12 hours, thoroughly shampoo the hair; rinse and use a fine-toothed nit comb, usually included in the package, to remove dead lice and nits from the hair.
  5. After treatment, use a fine-toothed nit comb to check the hair for live lice every 2–3 days for 2–3 weeks until sure that all lice are gone.
  6. If live lice are found 7 to 9 days after treatment, retreat with a second application of the same medication.

Warnings and Precautions:

  1. Malathion may cause stinging, especially if the scalp has open sores from scratching.
  2. Keep medication out of the eyes.
  3. Malathion is flammable; keep medication and wet hair away from heat sources such as hair dryers, electric curlers, cigarettes, or open flames.
  4. Pregnant and nursing mothers should use malathion only after consulting their physician.

Step 2: Consider additional household measures:

Head lice do not live long (less than 1–2 days) if they fall off a person and cannot feed; nits cannot hatch and usually die within a week if they are not kept at the same temperature as that found close to the human scalp. You do not need to spend a lot of time or money on housecleaning activities. Follow these steps to help avoid re-infestation by live lice or nits that may have recently fallen off the head or crawled onto clothing or furniture.

  1. To kill lice and nits that may have fallen or crawled off the head onto clothing or other articles, machine wash clothing, bed linens, and other items (e.g. towels, stuffed animals, comforters, blankets, etc.) that the infested person wore, slept on, or used during the 2 days before treatment. Use the hot water (at least 130°F) cycle. Dry the laundry using the high heat setting for at least 20 minutes. Items that are not washable can be dry-cleaned.ORstored in a sealed plastic bag for 2 weeks.
  2. Soak combs and brushes in hot water (at least 130°F) for 5–10 minutes.
  3. Vacuum the floor and furniture, particularly where the infested person sat or lay. However, the risk of getting infested by a louse or a nit that was attached to a shed hair that has fallen onto a carpet or furniture is very small. Head lice survive less than 1–2 days if they fall off a person and cannot feed; nits cannot hatch and usually die within a week if they are not kept at the same temperature as that found close to the human scalp. Spending much time and money on housecleaning activities is not necessary to avoid reinfestation by lice that have crawled or nits on shed hairs that may have fallen off the head. Do not use fumigant sprays; they can be toxic if inhaled or absorbed through the skin.

Step 3: Prevent Reinfestation:

Lice are spread most commonly by direct head-to-head (hair-to-hair) contact and much less frequently by sharing clothing or belongings onto which lice or nits may have crawled or fallen. Teach children to avoid types of play and other activities that may spread lice.

  • Avoid head-to-head (hair-to-hair) contact during play and other activities at home, school, and elsewhere (slumber parties, sports activities, camp, playground).
  • Do not share clothing such as hats, scarves, coats, sports uniforms, hair ribbons, or barrettes.
  • Do not share combs, brushes, or towels.
  • Do not lie on beds, couches, pillows, carpets, or stuffed animals that have recently been in contact with an infested person.

My child is under 6 years old and has been diagnosed with head lice. Can I treat him or her with malathion (Ovide* lotion)?

Before treating young children, ask the child’s physician for treatment recommendations. The safety and effectiveness of malathion lotion (Ovide*) has not been established by well controlled trials in children less than 6 years old. Malathion is contraindicated in children younger than 2 years of age.

Are treatment failures with malathion common?

No, however reinfestation can occur.

Is a second treatment needed?

Maybe. If live lice still are found after 7–9 days, a second treatment with malathion lotion may be given. Other family members should be checked for signs of infestation.

Does malathion kill head lice eggs?

Yes. The malathion lotion (Ovide*) available by prescription in the United States can kill some lice eggs.

*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 information 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 parasites described above or think that you may have a parasitic infection, consult a health care provider.

Page last reviewed: September 17, 2020