25Chemicals in Lice Products Linked to Health Problems in Children
Pyrethroids are a class of chemicals used in insecticides, including the most popular head lice medications. A new study in the Occupational and Environmental Medicine reports what many had feared for decades—that “exposure to certain pyrethroids, at environmental levels, may negatively affect neurobehavioral development by 6 years of age.”
Pyrethroids are neurotoxins. They work by disrupting the nervous systems of insects, killing them in the process. Health advocates have for years questioned the medical wisdom of putting neurotoxins on children’s scalps. 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.
Pyrethroid Chemicals in Lice Products: Study Results
There were three pyrethroid metabolites chemicals in lice products that showed up most often in the urine of mothers and their children—trans-DCCA, cis-DBCA, and cis-DCCA—for those that want to know. The conclusion of the study was that “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.”
This follows a 2015 study in Environmental Health that found that “Pyrethroid pesticides cause abnormalities in the dopamine system and produce an ADHD phenotype in animal models, with effects accentuated in males versus females. However, data regarding behavioral effects of pyrethroid exposure in children is limited.”
To summarize: One study found a correlation between elevated levels of pyrethroids in children and “abnormal” behavior; another found that animals exposed to pyrethroids develop ADHD-like behavior. Neither study proves a medical link between pyrethroids and behavioral change in children, but there is certainly reason for concern.
It should cause concern because pyrethroids remain the first line of defense against head lice recommended by many doctors. This is changing, but not necessarily due to health concerns. Multiple studies performed in recent years have found that most head lice in the United States and other countries are developing resistance to pyrethroids, so these neurotoxins that parents are putting on their children’s heads don’t even work.
“The ideal treatment of lice should be safe, free of toxic chemicals, readily available without a prescription, easy to use, effective, and inexpensive,” the AAP said. The article notes that the overall spending on lice treatment has risen to nearly $1 billion annually, with as many as 12 million children contracting head lice each year.