What Is the Strongest Thing To Kill Lice?

Medically Reviewed on 12/21/2021
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Pediculicides, particularly ivermectin lotion, are the strongest measures to get rid of a lice infestation.

Pediculicides or medications that kill lice are the strongest measures to get rid of a lice infestation. Of the various pediculicides, ivermectin lotion has emerged as one of the strongest solutions to get rid of lice.

  • A single application can kill the lice without any need for nit combing.
  • The drug was approved in 2012 by the U.S. Food and Drug Administration (FDA) as a pediculicide in people older than six months. This was based on the results of two clinical trials that included 765 adults and children older than six months.

These trials, however, compared the efficacy of ivermectin with placebos and not other pediculicides. Nonetheless, the advantages of a single application without the need for nit combing makes ivermectin lotion one of the most promising medication to kill lice.

The most suitable anti-lice treatment may depend on the person’s age, the severity of the infestation, history of using any pediculicides, and the presence of any underlying conditions, including allergies, seizures, psoriasis, and pregnancy.

What are the treatment options for lice infestation?

Pharmacologic treatment

Pharmacologic treatment for lice infestation includes drugs to kill lice (pediculicides).

  • Over-the-counter (OTC) mediations: These FDA-approved medications are available without the doctor’s prescription. They must be used carefully according to their label instructions. If lice infestation persists despite a full course of OTC medications, contact your healthcare provider.
    • OTC medications against lice infestation include:
      • Pyrethrins with additives (piperonyl butoxide): They are available under various brand names, such as Rid, triple X, A-200, Pronto, and R&C.
        • These medications can be used for adults and children older than two years.
        • Pyrethrins are naturally occurring compounds extracted from the chrysanthemum flower.
        • The added chemicals increase their efficacy against lice. 
        • Although they kill lice, they are not effective against lice eggs or nits. Thus, a repeat treatment is advised after 9 to 10 days to kill newly hatched lice before more nits are produced.
        • They are generally safe to use according to instructions.
        • They must be avoided if the person has ragweed or chrysanthemum allergy.
      • Permethrin lotion, one percent: They are available under the brand name Nix.
        • Permethrin is a synthetic compound that is chemically similar to pyrethrins.
        • Like pyrethrin, permethrin kills lice without killing nits. Thus, another treatment is required on day nine.
        • Permethrin lotion can be used in adults, children, and infants as young as two months.
  • Prescription medications: If you see crawling lice despite a full course of OTC medications, you may ask your doctor for a prescription against lice infestation. Make sure that you use them according to your doctor’s instructions.
    • FDA-approved anti-lice prescription medications include:
      • Ivermectin lotion, 0.5 percent: It is available under the brand name Sklice.
        • Ivermectin lotion (0.5 percent) can be used by adults and children who are aged at least six months.
        • Although ivermectin does not kill nits, it does seem to get rid of newly hatched lice (nymphs).
        • Besides ivermectin lotion, your doctor may prescribe oral ivermectin tablets to kill headlice.
        • Ivermectin tablets should not be used in pregnant females and children who weigh less than 33 pounds.
      • Benzyl alcohol lotion, five percent: It is available under the brand name Ulesfia lotion.
        • It is a safe and effective head lice treatment for adults and children aged as young as six months. It can, however, cause skin irritation.
        • Benzyl alcohol lotion cannot kill nits, and thus, a repeat treatment is recommended after seven days to kill the nymphs before more nits are produced.
      • Malathion lotion, 0.5 percent: It is available under the brand name Ovide.
        • Although it mainly targets live lice, it has some effect against nits (ovicidal) as well.
        • Because the ovicidal effect is partial, a second treatment after a week to nine days is recommended.
        • Malathion is a synthetic (organophosphate) compound that can cause skin irritation and even catch fire (flammable). Hence, avoid the use of hair dryers or other forms of heat styling, going near flames, and smoking after using malathion lotion until your hair is completely dry.
      • Spinosad, 0.9 percent topical suspension: It is available under the brand name Natrona.
        • Spinosad is a combination of two naturally occurring compounds (Spinosyn A and D) isolated from soil bacteria.
        • It can be used in adults and children aged as young as six months. It kills both live lice and their nits. Thus, a repeat treatment is generally not required unless crawling lice are seen a week after the initial treatment.

Nonpharmacologic treatment

These include treatments apart from medications to kill lice with remedies such as:

  • Fine-toothed combing:
    • The safest way to remove headlice that, however, involves a lot of time and patience.
    • Fine-toothed combs must be used after applying hair oil or a conditioner.
    • Use the comb about three to four times a week on wet hair to remove lice and nits.
    • Several inexpensive and effective nit combs are available in the market.
    • You do not need to buy the more expensive electronic combs to remove lice because they do not seem to have any added advantage.
  • Hot air treatment:
    • Involves killing the lice using a hot air device (AirAlle) by professionals.
    • They have claimed to kill both lice and nits with a single treatment.
  • Lice smothering:
    • Using petroleum jelly, mayonnaise, or olive oil has been suggested to kill lice by suffocating them. These, however, do not seem to have any proven efficacy.
    • They may temporarily make the lice less active. This may be falsely considered as though they have killed the lice.
  • Essential oils:
    • These oils (such as tea tree or Ylang Ylang oil) are proposed to kill head lice. They need to be used after dilution in a carrier oil, such as coconut oil.
    • Their efficacy and safety, however, are not proven.

Several unproven and potentially dangerous treatments have been promoted. They include the use of bleach, vodka, acetone, and even gasoline for killing lice. You must completely stay away from these remedies because they can cause a lot of harm.

Avoid using hairdryers at very high temperatures to kill lice. It can cause serious burns and damage to your scalp and hair. Avoid using hair dryers after lice treatment because some medications are flammable.


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Medically Reviewed on 12/21/2021
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American Academy of Dermatology. How to get rid of head lice when treatment fails. https://www.aad.org/public/diseases/a-z/head-lice-fails

Centers for Disease Control and Prevention. Parasites. https://www.cdc.gov/parasites/lice/head/treatment.html

Consumer Reports. Best Ways to Treat Head Lice. https://www.consumerreports.org/medical-conditions/preventing-and-treating-head-lice/

American Academy of Family Physicians. Head Lice. https://familydoctor.org/condition/head-lice/

Skerrett PJ. Treatment for head lice effective with one dose and no combing. Harvard Health Publishing. https://www.health.harvard.edu/blog/new-treatment-for-head-lice-effective-with-one-dose-and-no-combing-201211015484