Mandatory lice-checks in schools across the country are effective at identifying the pests, but this year professionals in 25 different states are on edge as to how they will confront the growing threat posed by drug-resistant head lice. According to a press release from Eurekalert, scientists have found that many lice populations are developing a strong defenses against the majority of common over-the-counter treatments.

Researchers presented the results of a comprehensive study on drug resistance in head lice at the 250^th National Meeting and Exposition of the American Chemical Society. The meeting gave forum to over 9,000 presentations on a wide range of topics, with discussions continuing into Thursday.

Dr. Kyong Yoon from Southern Illinois University at Edwardsville explains that the study is the first to gather lice samples from populations across the country. Yoon’s findings show that 104 out of 109 distinct lice populations had genetic mutations that increased their resistance to pyrethroids, a class of insecticides that is used both indoors and outdoors to keep mosquitos and other insects from destroying crops and spreading diseases.

Yoon discovered that lice with a specific gene, formed by a kdr mutation, were less affected by pyrethroids than previously thought. “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 that head lice don’t carry disease. They’re more of a nuisance than anything else.”

Residents of major states such as California, Texas, Florida, New York, and New Mexico will need to keep a close eye out for head lice and begin treating them early and aggressively. Drug resistance in pests is a global issue, and it is affecting more schools across the country each day.