If you have kids returning to school soon, get ready for some head scratching. A recent report from an American Chemical Society (ACS) meeting in Boston warns that head lice in at least 25 U.S. states are resistant to most over-the-counter treatments, Time.com reports.

Lice are tiny wingless insects that feed on blood through the scalp. Although lice don’t transmit other illnesses, the critters lay their eggs (called nits) in human hair, and can cause an infestation. The infestation leads to an itchy, irritated scalp, scratching and, in some cases, an annoying rash. (The lousy condition is especially common among young children, and, experts say, starts to peak once kids go back to school.)

According to researchers in the Biological and Environmental Sciences Program at Southern Illinois University, this year’s lice problem could be worse than ever. Scientists reported that they’ve found that most lice in the United States today carry one to three different gene mutations that are super-resistant to pyrethroids—the active ingredient in many over-the-counter (OTC) anti-lice treatments.

“It’s a really, really serious problem right now in the U.S.,” said study author Kyong S. Yoon, PhD, an assistant professor at Southern Illinois University, who’s been studying the insects since 2000.

Yoon noted that if the current OTC treatments don’t work, there are prescription-based products, such as ivermectin and spinosad, to dispatch the tenacious parasites.

Also, if you thought head lice were just a problem faced by white kids, think again. Studies show that over the last few years, lice have undergone an evolution, adapting their claws have so the tiny insects can better grab on to the curlier hair of black children. Click here for more information.