(BERLIN, Md.)- Strains of mutated head lice have build up resistant to most over-the-counter treatments in at least 25 states, including Maryland.

In a new study, the pesky parasites are increasingly becoming resistant to pyrethroids, the active ingredients in most OTC concoctions.

Southern Illinois University Edwardsville Professor Kyoung Yoon was on the research team that found the mutated lice. He said out of 109 parasites tested 104 were immune to the chemicals.

Worcester County School system officials tell WRDE, they have a plan in place, and they will check kids the first week of school.

Marsha Zuckerman is a retired teacher. She said she has dealt with the pesky parasites first-hand.

"If you don't get it taken care of it becomes a problem," Zuckerman said. "If you let it go untreated it can get bad."

Jennifer Hawkins said parents should be notified this year.

"I would hope they would be sending notes home to the parents the first week of school," Hawkins said.

Researchers said to kill the head lice you will now need a higher dosage of medicine.