Head lice resistant to over the counter medications, nature adapts

The trio of mutations – called kdr, for “knock down resistance” – affects the insect’s nervous system and makes them less sensitive to the insecticide chemicals that are found in lice treatments and also in mosquito repellant or fly spray, for example.

The finding doesn’t mean you can’t kill lice with pyrethroids, Yoon said. Others-New York, New Jersey, New Mexico and Oregon-had up to three mutations.

There are other chemicals, such asivermectin or spinosad, which are available by prescription, that can kill head lice, but they’re not as safe or as gentle as the pyrethroids that doctors and schools currently recommend.

In the latest study, researchers found lice with all three genetic mutations in 25 states, including California, Texas, Florida and Maine.

They found that 104 out of 109 lice populations had high levels of gene mutations, which have been linked to resistance to pyrethroids.

Of the 30 states studied, Michigan was the only one where the remedy still works, while four others showed lice to still be somewhat vulnerable to the insecticide.

Using pyrethyroids is the most common treatment approach for combating head lice.

“It’s a really, really serious problem right now in the U.S.”, Yoon told Time.

Dr Yoon said why lice haven’t developed resistance there is still under investigation.

And this is not necessarily new; Pyrethroid-resistant lice were first discovered in Israel as far back as the 1990s; furthermore, Yoon was actually one of the first researchers to report on the phenomenon of pyrethroid-resistant lice in the United States, which would have been in Massachusetts in 2000.

“If you use a chemical over and over, these little creatures will eventually develop resistance”, Yoon said in a statement.

“Now we have a group of new chemistries and all these active ingredients don’t share the same mode of action”, Clark explained. With three new treatments released at about the same time, it would be very difficult for the bugs to mutate in a way that would resist all of them. When these chemicals were offered over-the-counter, it led to overuse, both scientists said. Head lice do not have wings and cannot jump.

The Centers for Disease Control and Prevention as many as 12 million American school children between the ages of 3 and 11 get them each year.

And there are worse things.