A disturbing new study has linked a common chemical found in head lice treatments to behavioral difficulties in children. 
 
 The research, which was published in the journal Occupational & Environmental Medicine, found that children who had higher levels of certain pyrethroids — which are synthetic chemicals used in insecticides like head lice treatments and some mosquito repellents — in their system were more likely to display abnormal behaviors at age 6 than those who didn’t. 
 
 Pyrethroids work by damaging the nerves of insects, killing them in the process, and scientists wanted to see if they had a negative impact on children as well. (Permethrin, an active ingredient in the most popular drugstore lice treatments, is a pyrethroid.) For the study, the researchers measured levels of five pyrethroid metabolites in the urine of women in the early stages of pregnancy and, later, in their 6-year-olds to see if there was a link between being exposed to the chemical in utero and childhood, and behavior that could suggest neurodevelopmental damage. 
 
 Nearly 300 women filled out a questionnaire about socioeconomic factors, lifestyle, their child’s behavior, and various things their child had been exposed to. Psychologists visited the families at home to do behavioral assessments of the children, and also took urine and dust samples. 
 
 Behavior was rated using the Strengths and Difficulties Questionnaire, a validated behavioral screening test for children, with a focus on altruism (how social children are), internalizing disorders (the inability to share problems and ask for help), and externalizing disorders (being defiant and disruptive). 
 
 Three of the pyrethroid metabolites showed up most often in the urine of mothers and their children: trans-DCCA, cis-DBCA, and cis-DCCA. 
 
 Here’s what researchers determined: Mothers with higher levels of cis-DCCA in their urine during pregnancy were more likely to have children with a higher risk of internalizing behaviors. Higher levels of another metabolite, 3-PBA, in the children’s urine was linked with a higher risk of externalizing behaviors. Overall, children with the highest levels of metabolites in their urine were three times more likely to have abnormal behavior than those with lower levels. As a result, the researchers concluded that pyrethroids might alter neurochemical signaling in the brain. 
 
 The news is understandably disturbing for parents who have treated their children with pyrethroids for lice — and there are a lot of them. The Centers for Disease Control and Prevention estimates that up to 12 million head lice infestations happen each year among children aged 3 to 11. Lice are parasites that live in human hair, eyelashes, and eyebrows and feed on the blood of their host, and they’re not easy pests to get rid of. Hence, the common use of chemical shampoos and treatments for lice infestations — many of which contain pyrethroids. 
 
 Before you panic, know this: The study found that there was a correlation between pyrethroids and behavioral issues in children — not a causation. That means they determined that children who have behavioral issues also have high levels of certain pyrethroids in their system, but didn’t actually find that using pyrethroids causes behavioral problems in children. 
 
 “The findings should be considered preliminary and prompt more rigorous studies,” Amesh A. Adalja, MD, a board-certified infectious disease physician and affiliated scholar at the Johns Hopkins Center for Health Security, tells Yahoo Beauty. 
 
 Shahrouz Ganjian, MD, a board certified pediatrician at Providence Saint John’s Health Center in Santa Monica, Calif., tells Yahoo Beauty that he’s not shocked by the findings. “In the past 15 years, there’s been a lot more research that has found pesticide exposure is linked to ADHD in boys and pediatric cancer,” he says. The study that found a link between ADHD and pesticides was published in the journal Environmental Health. It found a link between pyrethroid pesticide exposure and ADHD, particularly in the areas of hyperactivity and impulsivity. While girls were affected, the link was stronger in boys. However, this was also a correlational study. 
 
 Pyrethroids are among the most common treatments for lice, but other compounds can be used, like alcohol-based treatments and an anti-parasitic drug called ivermectin, Adalja says. However, pyrethroids are “the main recommended treatments for lice,” he adds. Ganjian also recommends Sklice lice treatment, which doesn’t contain pyrethroids and Licefreee, which he calls “more natural.” ||||| 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. 
 
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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.
– Here's something else not to like about lice, mosquitoes, and fleas. An insecticide used to kill them—pyrethroids—might be linked to behavior issues in children as young as 6, a French study suggests. The researchers, noting the effects the chemical had on the nervous systems of insects, wondered how it affected humans, notably children. They tested the urine of about 300 pregnant women and, six years later, their children, according to the study published in Occupational & Environmental Medicine. Children with the highest levels of pyrethroids in their urine were three times more likely to have behavioral problems than kids with lower levels. The problems might be external (kids being defiant or disruptive) or internal (a reluctance to ask for help) depending on the specific type of pyrethroid they were exposed to, the study said. "The pesticide class studied are considered 'safe' pesticides and this study is cause for concern as to how safe it really is," says a child psychatrist at Lenox Hill Hospital in New York City who reviewed the findings, per HealthDay News. But he cautions that the study finds only a correlation, not cause and effect. Along those lines, a doctor at Johns Hopkins characterizes the study as preliminary and says it should be followed up by further research, reports Yahoo. Still, a pediatric behaviorialist not involved with the research recommended that pregnant women use "common sense" when using insecticides and look for products that don't contain pyrethroids. (In an awful story out of Massachusetts, police say a homemade lice remedy proved fatal for a girl.)