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.” ||||| 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.
– 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.)