Head lice are a giant nuisance -- as many as 12 million American school children between the ages of 3 and 11 get them each year, according to the Centers for Disease Control and Prevention. And to make matters worse, researchers continue to find evidence that the tiny pests are becoming genetically resistant to common treatments that people use to battle the bugs. 
 
 A new study finds that lice in at least 25 states have developed resistance to an ingredient found in over-the-counter remedies that are widely recommended by doctors and school officials. The research is being presented Tuesday at a meeting of the American Chemical Society (ACS). 
 
 Researchers from Southern Illinois University gathered lice samples from 30 states, with the help of a network of public health workers. 
 
 "We are the first group to collect lice samples from a large number of populations across the U.S.," explained Kyong Yoon, Ph.D., in a press release. "What we found was that 104 out of the 109 lice populations we tested had high levels of gene mutations, which have been linked to resistance to pyrethroids." 
 
 Pyrethroids are a family of insecticides widely used to control pests. They include permethrin, the active ingredient in some of the most popular lice treatments on drugstore shelves. 
 
 Evidence of widespread pyrethroid-resistant lice has been building for years. Yoon was among the first to report on the phenomenon in the United States 15 years ago, the press release notes, when he tested lice samples for three genetic mutations known collectively as "knock-down resistance." 
 
 The mutations affect an insect's nervous system and desensitize it to pyrethroids. Since that report came out, Yoon has expanded his survey. 
 
 In the latest study, researchers found lice with all three genetic mutations in 25 states, including California, Texas, Florida and Maine. 
 
 Having all three genetic mutations means that these lice populations are the most resistant to pyrethroids. 
 
 Intermediate levels of pyrethroid-resistance were found in four states: New York, New Jersey, New Mexico and Oregon. 
 
 Of the 30 states involved in the study, only Michigan had a population of lice that was still largely susceptible to treatment with pyrethroids. Researchers are investigating why these bugs have not developed a resistance. 
 
 So what's a parent to do? 
 
 The American Academy of Pediatrics advises that in areas with known resistance to an over-the-counter treatment, "parents should involve their pediatrician for treatment with a prescription medication such as spinosad or topical ivermectin." 
 
 These newer medications are sold as Natroba (spinosad 0.9% topical suspension) and Sklice (ivermectin lotion, 0.5%), respectively. 
 
 But over time, they could be at risk of the same problem as lice populations continue to evolve, cautions Yoon. "If you use a chemical over and over, these little creatures will eventually develop some resistance," he said. 
 
 The National Pediculosis Association, a non-profit group behind the website HeadLice.org, also offers suggestions for frantic parents who find that a lice treatment product hasn't worked. Stop using the product, and don't follow it with another product, the group says, to avoid exposing the child to too many pesticides. 
 
 It also says parents should avoid use of Lindane (a prescription treatment that can cause serious side effects), kerosene or pet shampoos. 
 
 The Association advises manually removing the nits, or lice eggs, with a nit-removal comb. In many cities, professional treatment services have entered the market to help families deal with cases of head lice either at home or in special salons. 

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 / Updated / Source: TODAY By Linda Carroll 
 
 As many parents know, kids are increasingly bringing home some very unwanted guests — head lice. The pesky parasites are now a much worse problem than in years past, with strains resistant to most common treatments found in at least 25 states. 
 
 The spread of an ultra-strain of lice means you'll need to use a higher dose of chemical to kill them. Shutterstock 
 
 Lice — and other insects — are increasingly becoming resistant to pyrethroids, the active ingredients in most OTC concoctions, according to Kyong Yoon, an assistant professor at Southern Illinois University—Edwardsvillle. Yoon was part of the research team that initially discovered the new ultra-resistant strains, publishing their results in August, 2015. 
 
 Yoon and his colleagues wanted to know how widespread these resistant strains were. 
 
 “We collected 109 lice populations and 104 had high levels of gene mutations,” Yoon reported at the annual meeting of the American Chemical Society in August. 
 
 Researchers are finding that head lice that are becoming resistant to OTC treatments. Red states: 100 percent of the tested lice were resistant. Orange states: 50 to 90 percent of lice were resistant. Yellow states: 1 percent to 49 percent were resistant. Blue states: Data hasn't been analyzed yet. White states haven't been tested. Southern Illinois University-Edwardsville 
 
 Pyrethroids, which are synthetic versions of a chemical found in chrysanthemums, lock onto receptors in insect nervous systems, paralyzing the creepy crawlies and eventually killing them. 
 
 You're going to need a bigger dose 
 
 But over the years, Yoon said, lice have evolved in such a way that the chemicals no longer fit neatly into the receptors, thereby squashing the chemical’s bug-killing ability. 
 
 Researchers at Southern Illinois University suggest that head lice populations in at least 25 states have developed resistance to over-the-counter treatments. NBC News medical contributor Dr. Natalie Azar addresses parents’ concerns on TODAY as kids get ready to return to school. TODAY 
 
 The finding doesn’t mean you can’t kill lice with pyrethroids, Yoon said. But you will need a higher dose. 
 
 Pediatric dermatologist Dr. Robin Gehris says despite the finding, she still believes in OTC treatments. While they may be somewhat less effective, they still work much of the time, she said. 
 
 In some cases, the treatments don’t do a thorough job because parents don’t use them as directed. 
 
 If you’re using an OTC treatment, be sure to apply it a second time five to seven days later, Gehris said. Some therapies don’t kill all the eggs the first time, and those survivors will hatch about a week later. 
 
 Also, be sure to leave the treatment on long enough. 
 
 Sometimes therapies fail because they’re rinsed out too soon, Gehris said. “You want to leave it on overnight with a shower cap,” she added. “A common reason for failure is that the children don’t like the smell and want to wash it off soon.” 
 
 If your child still has lice after all that, you may need to see your pediatrician to get a prescription for one of the treatments that lice haven’t yet become resistant to, Gehris said. 
 
 Home remedies fail? 
 
 As for home remedies, there’s no evidence that any work, Gehris said. She traces their popularity to advice given by a multitude of school nurses. 
 
 “Olive oil, mayonnaise, Vaseline, these are all treatments I wouldn’t recommend,” she said. “But I hear school nurses recommending them all the time.” 
 
 Yet, Gehris doesn’t completely reject those therapies. “If you want to use mayonnaise as an adjunct, I’m OK with that,” she explained. “Theoretically, it could work if you put it on thickly enough that the lice aren’t able to breathe. But it’s hard to imagine that you could get it on thickly enough to really do the trick.” 
 
 Nit picking doesn't work? 
 
 And bad news for parents who rely solely on “nit pickers,” or commercially available fine-toothed combs — there’s no evidence suggesting combs are successful, said Dr. Bernard Cohen, a professor of pediatrics and dermatology at the Johns Hopkins Children’s Center. “There have been a couple of nice studies showing that nit picking doesn’t really work,” he said. 
 
 Hot air therapy may appeal to parents who don’t want to treat their kids with chemicals, Cohen said, adding the Food and Drug Administration has approved devices for this purpose. The downside, he said, is children need to be under heat for 30 minutes or so. 
 
 No hair, no lice 
 
 Ultimately, if nothing else works, there’s one last option that is proven to be 100 percent effective — even if kids generally hate it, Cohen said. “That’s what I would call ‘destruction of habitat,’” he explained. “If you destroy an organism’s habitat, then they are dead meat.” 
 
 What he’s suggesting, in plain English, is shaving the child’s head. No hair, no lice. 
 
 This story was originally published in August. 

 BOSTON, Aug. 18, 2015 -- For students, the start of the school year means new classes, new friends, homework and sports. It also brings the threat of head lice. The itch-inducing pests lead to missed school days and frustrated parents, who could have even more reason to be wary of the bug this year. Scientists report that lice populations in at least 25 states have developed resistance to over-the-counter treatments still widely recommended by doctors and schools. 
 
 The researchers are presenting their work today at the 250th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society. The meeting features more than 9,000 presentations on a wide range of science topics and is being held here through Thursday. 
 
 "We are the first group to collect lice samples from a large number of populations across the U.S.," says Kyong Yoon, Ph.D. "What we found was that 104 out of the 109 lice populations we tested had high levels of gene mutations, which have been linked to resistance to pyrethroids." 
 
 Pyrethroids are a family of insecticides used widely indoors and outdoors to control mosquitoes and other insects. It includes permethrin, the active ingredient in some of the most common lice treatments sold at drug stores. 
 
 Yoon, who is with Southern Illinois University, Edwardsville, explains that the momentum toward widespread pyrethroid-resistant lice has been building for years. The first report on this development came from Israel in the late 1990s. Yoon became one of the first to report the phenomenon in the U.S. in 2000 when he was a graduate student at the University of Massachusetts, Amherst. 
 
 "I was working on insecticide metabolism in a potato beetle when my mentor, John Clark, suggested I look into the resurgence of head lice," he says. "I asked him in what country and was surprised when he said the U.S." 
 
 Intrigued, Yoon followed up on the lead and contacted schools near the university to collect samples. He suspected that the lice had developed resistance to the most common insecticides people were using to combat the bugs. So he tested the pests for a trio of genetic mutations known collectively as kdr, which stands for "knock-down resistance." kdr mutations had initially been found in house flies in the late '70s after farmers and others had shifted to pyrethroids from DDT and other harsh insecticides. 
 
 Yoon found that many of the lice did indeed have kdr mutations, which affect an insect's nervous system and desensitize them to pyrethroids. Since then, he has expanded his survey. 
 
 In the most recent study, he cast the widest net yet, gathering lice from 30 states with the help of a broad network of public health workers. Population samples with all three genetic mutations associated with kdr came from 25 states, including California, Texas, Florida and Maine. Having all the mutations means these populations are the most resistant to pyrethroids. Samples from four states -- New York, New Jersey, New Mexico and Oregon -- had one, two or three mutations. The only state with a population of lice still largely susceptible to the insecticide was Michigan. Why lice haven't developed resistance there is still under investigation, Yoon says. 
 
 The solution? Yoon says that lice can still be controlled by using different chemicals, some of which are available only by prescription. 
 
 But the situation also offers a cautionary tale. "If you use a chemical over and over, these little creatures will eventually develop resistance," Yoon says. "So we have to think before we use a treatment. The good news is head lice don't carry disease. They're more a nuisance than anything else." 
 
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 A press conference on this topic will be held Tuesday, Aug. 18, at 1:30 p.m. Eastern time in the Boston Convention & Exhibition Center. Reporters may check-in at Room 153B in person, or watch live on YouTube http://bit. ly/ ACSLiveBoston . To ask questions online, sign in with a Google account. 
 
 The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 158,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio. 
 
 To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org. 
 
 Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society. 
 
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 Title 
 
 Pyrethroid-resistant head lice: Updated status, lessons learned and management in the 21st century 
 
 Abstract 
 
 Since the resurgence of human head lice in the 1990s, many cases of pyrethroid resistance known as the knockdown resistance (kdr) in global populations of head lice have been reported. This genetically heritable kdr, mainly conferred by three point mutations (M815I, T917I and L920F) in the para-orthologous voltage-sensitive sodium channel gene, is a major attribute of pyrethroid-resistant head lice. Using a tier system of three molecular resistance detection protocols (quantitative sequencing, the real-time PASA and the serial invasive signal amplification reaction), kdr frequencies of field populations have been successfully estimated with considerations of sample collection conditions and accuracy of each genotyping method. Recently, quantitative sequencing (QS) suitable for a primary resistance monitoring tool to screen a large number of louse populations has been utilized to generate a detailed kdr allele frequency map that will illustrate distribution of kdr possessing head lice in the US. For this, our on-going study aims to collect samples from both urban and suburban areas. Preliminary results showed that 104 out of 109 populations were 100% resistant in the MI-TI-LF mutations in states ranging from Maine, Florida, Texas, Minnesota and California. Intermediate levels of resistance were found in 4 states (NJ, NM, OR, and NY). The only completely susceptible population was found in MI.
– Head lice might be a bit harder to nit, er, nip in the bud this year: A study out of Southern Illinois University-Edwardsvillle finds the pests have developed resistance to popular over-the-counter medications in at least 25 states. Kyong Yoon, who helped discover ultra-resistant strains, collected 109 samples of lice from 30 states. "What we found was that 104 out of the 109 lice populations we tested had high levels of gene mutations, which have been linked to resistance to pyrethroids," he says in a press release. Pyrethroids—a family of insecticides including permethrin, the active ingredient in common lice treatments—kill insects by latching onto receptors in their nervous systems. But lice have evolved so the chemicals no longer find a perfect fit. That doesn't mean the treatments won't work, but you'll need a higher dose. CBS News reports 12 million American kids, ages 3 to 11, get lice each year. Yoon specifically tested the samples for a trio of genetic mutations known as kdr. Samples in 25 states were most resistant with all three. Samples from four states, including New York, New Jersey, New Mexico, and Oregon, had one, two, or three. Michigan was the only state where lice hadn't developed resistance. A dermatologist recommends following medication directions, which means applying a treatment a second time, five to seven days after the first. If the first treatment didn't kill all the lice eggs, they'll hatch after a week, reports Today. If all else fails, a pediatrician can prescribe a treatment lice aren't resistant to. What to avoid: Home remedies like olive oil and mayonnaise, since there's no proof they work. The same goes for fine-toothed combs, an expert says. The one all-natural treatment that is proven effective: destroying the habitat, aka shaving your head. (Home lice remedies can be deadly.)