Resistant Lice: Lice In 25 States Are Resistant To OTC Treatment, Study Shows

Resistant lice are now living in 25 states, and with school starting back, this may be an important issue for parents, especially those of school-aged children.

According to a new study, researchers found that a form of lice, which have now been found in nearly half of the United States, is resistant to over-the-counter treatments.

The American Chemical Society in Boston released the details regarding the mutant lice earlier this week. The research was presented at the 250th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society. The meeting is being held through Thursday, and will feature over 9,000 presentations on numerous scientific topics.

“We are the first group to collect lice samples from a large number of populations across the U.S.,” Kyong Yoon, Ph.D., a member of the research group from Southern Illinois University, Edwardsville, said, according to a press release. “What we found was that 104 out of the 109 lice populations we tested had high levels of gene mutations, which have been linked to resistance to pyrethroids.”

Pyrethroids are widely used indoors and outdoors to control mosquitoes and other insects. Permethrin, the most commonly used ingredient in the over-the-counter lice treatments that are commonly recommended by doctors and teachers, is also found in the pyrethroids.

The first reports of the mutant lice came in the late 1990s in Israel. As a graduate of University of Massachusetts, Amherst, Yoon became the first to recognize the phenomenon in the United States.

“I was working on insecticide metabolism in a potato beetle when my mentor, John Clark, suggested I look into the resurgence of head lice,” he recalled. “I asked him in what country and was surprised when he said the U.S.”

Yoon later collected samples from 30 states, and analyzed them for knock-down resistance, or kdr mutations, which affect an insect’s nervous system and desensitize them to pyrethroids. Luckily, because lice don’t carry disease, they become more of a nuisance than anything.

“If you use a chemical over and over, these little creatures will eventually develop resistance,” Yoon said. “So we have to think before we use a treatment. The good news is head lice don’t carry disease. They’re more a nuisance than anything else.”

The lice can still be treated by using different chemicals, some of which are found in prescription treatments.

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