Millions of people worldwide know about that incessant irritating itch caused by head lice. The creepy crawlies are hard to get rid of, and the best plan of attack often involves an arsenal of specialized combs, shampoos and medicated topical treatments to eradicate the nasty pests.

Now sufferers may have one more tool, thanks to a recent study that looked at ivermectin [ī-vər-ˈmek-tən], an antiparasitic drug most often used for treating human river-blindness and animal parasites like scabies.

Published in The New England Journal of Medicine, the study compared an oral form of the medication with a lotion containing the insecticide malathion, a commonly prescribed treatment for head lice. Researchers worked with more than eight-hundred people in over three-hundred-and-fifty households all around the world. Even after being treated with over-the-counter creams or prescription lotions containing malathion, all participants still had head lice.

So researchers were randomly placed in two groups, one getting two doses of an ivermectin pill plus an inactive lotion, and the other receiving malathion lotion plus a placebo pill. After two weeks, ninety-five percent of the ivermectin group was lice-free, compared with eighty-five percent of the malathion group.

The researchers explained that the ten percent difference was in fact significant, not in suggesting that the ivermectin should be a first-choice remedy or a replacement for malathion, but rather as an adjunct treatment should the malathion not work, or, as in some rare cases with either one, cause a bad reaction. The doctors advised a cautious approach, noting that the cure and any possible side effects should never be more harsh than the original problem.