Mutant Lice: Are Your Treatments Effective?

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By News Team on October 19, 2015

Treating lice is a tricky task, especially when children are involved. Unfortunately, a recent study determined that it may get even trickier in the coming years.

During an August meeting of the American Chemical Society, Kyong Yoon, Ph.D., associate professor at Southern Illinois University, released his findings that lice in at least 25 states have mutated to become highly resistant to ingredients of over-the-counter lice treatments.

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

Intrigued, Yoon followed up on the lead and contacted schools near the university to collect samples. He suspected that the lice had developed resistance to the most common insecticides people were using to combat the bugs.

He tested the pests for a trio of genetic mutations that affect an insect’s nervous system and desensitize them to pyrethroids – a common ingredient in over-the-counter treatments.  

Yoon was surprised to find that many of the lice he tested did have those mutations, which meant that those lice populations were highly resistant to pyrethroids.  

Based on that finding, Yoon decided to expand his research to study lice samples from all over the country, most recently looking at lice samples spanning 30 states.

Samples from 25 of those states – including Virginia – proved to have those same three mutations indicating a high resistance to over-the-counter treatments.

Resistance is kind of natural development in the evolutionary cycle, so it's natural that the lice are going to try and find a way to survice. It is important that we have to keep up with new medicines to counteract that.

Over-the-counter shampoos are still the most inexpensive and common first line of treatment. If those prove ineffective, however, lice can still be controlled by using different chemicals, some of which are available only by prescription.

According to the American Academy of Dermatology, other important methods to keep in mind when combating head lice are lice combs; checking close family and friends for lice every day for 10 to 15 days to prevent lice from spreading; and washing all clothing, bedding, stuffed animals and pillows.

"If your at-home treatments are not working, you are encouraged to visit your primary care physician or dermatologist. Whichever treatment you choose, Yoon’s findings offer a cautionary tale. “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.”

For more information, see Carilion Clinic’s health and wellness page about the diagnosis and treatment of head lice.

This article was reviewed by Carilion Children's physicians.