Study shows lice in at least 25 states now resistant to common treatments

BOSTON, MA (KTRK) -- New research suggests head lice are getting even harder to kill.

A study conducted by researchers at Southern Illinois University suggests there is a new species of mutant lice that are resistant to most over-the-counter treatments.

"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," said Kyong Yoon, Ph.D., who conducted the research.

Pyrethroids are a type of insecticide used in many lice treatments.

Tips to keep lice out of your child's head.

Yoon said he gathered head lice from 30 states for his study, and he discovered lice in 25 of those states, including Texas, had development resistance to treatments such as RID Lice Killing Shampoo and Nix Cream Rinse.

"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."

Yoon is presenting his findings this week at the 250th National Meeting & Exposition of the American Chemical Society.