The era of the super lice has begun and it will be itchy.

The authors of a recent study published this March in the Journal of Medical Entomology analyzed the genes of human head lice (Pediculus humanus capitis) found across 48 states. They were specifically looking for a set of three mutations that allow lice to survive the most common over-the-counter treatments used to get rid of them, a class of insecticides known as pyrethroids. In 42 out of 48 states, the bugs tested had on average all three mutations, with the remaining six containing lice that generally had at least one or two mutations. Of the 138 different locations where the lice were taken from, only one in Michigan had lice that didn’t contain any of the three resistance genes.

"What it's telling us is that, right now, these over-the-counter products aren't nearly as effective as they used to be," senior author Dr. John Clark, a professor in the Department of Veterinary and Animal Sciences at the University of Massachusetts, told Live Science this August.

The findings by Clark and his team are only the latest to show how widespread the super lice problem has become. An earlier 2014 study conducted by many of the same authors, for instance, found that these lice were dominant in 12 states and 3 Canadian provinces; a 2015 report increased the tally to 25 states. Other research has documented the steady trend of pyrethroid resistance among hundreds of different insects, including bed bugs and house flies. As far as we can tell, head lice started becoming increasingly resistant to pyrethroids sometimes around the 1990s, and nowadays these insecticides may kill as little as 25 percent of lice during treatment.

"There is nothing unique about lice becoming resistant to the pyrethroids," Clark explained. "We have over 300 different insects that have become resistant to the pyrethroids, and many of those insects became resistant by acquiring these mutations exactly as the head louse has done."

Alarming as this trend is, though, there’s no need to be worried about a lice uprising just yet. Recently developed prescription medications like Natroba and Ulesfia do appear to still work tremendously well against them, though the threat of eventual resistance is certain the more of them we use.

Elsewhere, there are other OTC products like LymeMD, which don’t use insecticides at all, that have shown some promise as a reliable anti-lice treatment. Rather than chemically attack their nervous system, as pyrethroids do, the treatment, a silicone-based gel often used in cosmetics, physically prevents lice from excreting water and lubricates the hair so lice and their eggs can be more easily removed by a specialized comb, the latter treatment still being an important part of combatting a lice infestation.

Just don’t count on any natural treatments that promise to “suffocate” the bugs — those definitely don’t work.

Source: Gellatly K, Krim S, Palenchar D, et al. Expansion of the Knockdown Resistance Frequency Map for Human Head Lice (Phthiraptera: Pediculidae) in the United States Using Quantitative Sequencing. Journal of Medical Entomology. 2016.

Read More:

A Recent Outbreak Of Lice Among Teens Has Many Blaming Selfies. Read here.

How A Home Remedy For Head Lice Killed An Infant Girl In Massachusetts. Read here.