As students file back into the classroom this month, parents need to be extra diligent about keeping lice at bay. According to a study published in the Journal of Medical Entomology, a mutated type of lice that is resistant to permethrin-containing products and other common remedies has been found in 48 states—everywhere but Alaska and West Virginia, which did not submit lice for testing.
Researchers found a correlation between the reduced effectiveness of permethrin formulations and an increase in the kdr-type mutation in lice. According to the study, from 1984 through 1995, permethrin “consistently showed 96% to 100% effectiveness” in containing lice. By 2001 the rate was down to 80% and “subsequent reports of effectiveness have ranged from 28% to 55%, even where treatments have been augmented by nit combing.”
Pyrethrin formulations have been a standard treatment for lice since they were introduced in 1945 as a natural product made from chrysanthemums. Permethrin, a synthetic pyrethroid, was introduced in the 1980s.
The authors of the study cautioned that the results could be skewed due to the small sample size and the fact that the lice were collected mostly from metropolitan and urban sites. “The actual level of susceptibility could be higher than what was reported,” they said.
According to the CDC, the standard treatment for lice is still over-the-counter products like Nix or Rid. It is important to follow the package instructions carefully and to re-treat if necessary. To prevent lice, children should be taught not to share combs, hats, or anything else that could spread the parasites.
Nix Ultra Super Lice Treatment claims to “kill super lice.” According to the website, it is “specially designed to eliminate hard-to-kill Super Lice, which have developed resistance to many traditional lice treatments.” It works by suffocating the lice with dimethicone. The site also has a handy lice tracker, so you can check the current “lice incidence level” in your area.