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Study Finds Drug Kills Most Head Lice

Content provided by the Faculty of the Harvard Medical School

A newer drug appears to work well against head lice, researchers report. The new study used a lotion made with ivermectin, an insecticide. Researchers randomly divided 765 children who were infested with head lice into 2 groups. One group received ivermectin lotion. The other got a placebo containing no medicine. The lotions were applied to the hair and left on for 10 minutes before rinsing. A day later, 95% of the ivermectin group and 31% of the placebo group were louse-free. Researchers also checked at day 15 because louse eggs may hatch after treatment. At that point, 74% of the ivermectin group and 18% of the placebo group still had no lice. Researchers said current treatments, such as permethrin and pyrethrin, are only about 50% effective. Lice also have been gaining resistance to these treatments. Ivermectin is approved for other uses, but doctors can prescribe it for head lice. The New England Journal of Medicine published the study. An editorial in the issue said doctors should still prescribe standard treatments first and malathion second. The authors said we need to know more about ivermectin's long-term safety. HealthDay News wrote about the study October 31.

What Is the Doctor's Reaction?

If you've ever had a child with head lice — or if you've ever had lice yourself — you know it can be a big deal. Here are just some of the reasons that head lice matter:

  • Stigma – Having lice is often viewed as an indication of poor hygiene. But this is a myth.

  • Misguided treatment – False claims and misunderstanding about the head lice often lead to treatments that are dangerous or don't work. Examples include excessive and even risky medicine use and repeated hair shaving.

  • Occasional medical effects – Itching and scratching may lead to bacterial skin infections. Rarely, lice transmit Bartonella quintana, the bacteria that cause "trench fever." This infection is marked by high fever, headache, bone pain and a rash. It first was described in World War I soldiers.

  • Expense – The estimated cost of head lice in the U.S. is $1 billion each year! That includes the medical costs of treating head lice and the indirect costs, such as parents missing work when their kids aren't allowed to return to day care or school.

To make matters worse, lice increasingly are becoming resistant to standard treatments.

Given these realities, news about an easy and effective treatment for head lice may be important.

The New England Journal of Medicine published the results of a new study that tested ivermectin as a treatment for head lice. The U.S. Food and Drug Administration approved the treatment for head lice in February, but ivermectin is not the usual first choice of treatment. It's mainly used as an oral medicine for parasitic worm infections. So this research looked at a new way to use an old medicine.

The study included 765 children and adults who were infested with head lice. They were randomly assigned to receive ivermectin lotion or a placebo lotion. The placebo looked the same but contained no medicine. Each lotion was applied to the hair and scalp once for 10 minutes. Household contacts were treated only if they were also found to have lice.

The results were impressive:

  • Lice were gone 2 days after treatment for 95% of those treated with ivermectin lotion (and just 31% with the placebo).

  • By day 15, the cure rates were 74% for ivermectin and 18% for placebo.

  • Side effects were minor and the same in both groups.

Assessing the cure rate after 2 weeks is important because eggs laid before treatment may not hatch for 7 to 10 days. While the cure rate was not 100% at 2 weeks, that's common even with other highly effective treatments. It could be partly related to poor application of the lotion or to a second infection.


What Changes Can I Make Now?

Try to get past the "ick" factor. Lice may seem disgusting, but they are rarely dangerous. And they are usually easy to treat. If you or your child has head lice, here's what you can do:

  • Use a medicine recommended by your doctor, such as:

    • Permethrin

    • Pyrethrin

    • Malathion

    • Lindane

    • Benzyl alcohol lotion

    • Spinosad

    • Ivermectin (as described in this study)

  • Treat again 7 to 10 days after the first treatment if your doctor or pharmacist recommends it.

  • Comb the hair to remove nits (eggs).

  • Wash sheets, pillowcases or clothing with hot water and a heated dryer if they have come into contact with an infested person's head. Brushes, combs, hair accessories and hats should be washed in hot water as well.

Here's what you need not do:

  • Shave the person's head

  • Isolate the person – It's not even clear that keeping a child home from school because of head lice is necessary. But most U.S. schools and day care programs have policies that require kids with head lice to stay home.

  • Coat the hair in petroleum jelly or olive oil –You may be told this will suffocate the critters, but it hasn't been well studied. Besides, there are more effective options.

  • Hire industrial cleaners to "sterilize" your home – Lice require a blood meal every few hours. They don't last long on non-living surfaces, such as countertops or floors.

Reference: Skin, Hair and Nails section on Better Medicine


Did You Know?

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True or false? Head lice can often be found behind the ears and at the hairline at the back of the scalp.