Researchers are warning parents about a "super-strain" of head lice that is apparently resistant to over-the-counter treatments.
Of the states tested, 42 of the 48 report that 100 percent of the lice they tested have evolved to become resistant to pyrethroids and pyrethrins, the active ingredients in most over-the-counter head lice medications, reports Today. The study was published in the medical publication, Journal of Entomology.
According to study co-author Kyong Sup Yoon, "This mutation makes them somewhat insensitive. But in most cases pyrethrins and pyrethroids can still kill lice with the mutation, if you apply way more of the compound."
In plain English that means the lice are not immune to the treatment, it just takes more of it to kill them.
New Mexico and North Dakota found 50 to 99 percent of the lice had evolved, while Oregon, Michigan, New Jersey and New York had “mixed results with some testing sites at 100 percent and others less,” reports Independent Journal Review. Alaska and West Virginia are the only two states to have not yet been tested.
Dr. Robin Gehris, chief of pediatric dermatology at the Children’s Hospital of Pittsburgh, says the findings “are actually kind of scary.” She suggests giving children a double dose of the treatments.
"Treat the entire head and leave it on for a few hours and then repeat a week later," she suggests. "If you still see things moving after the second treatment it's time to call the doctor."
Gehris also said there is no evidence that home remedies, such as olive oil, mayonnaise and petroleum jelly, actually work.
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."