NIX Lice Treatment

NIX lice treatment is a very popular product marketed to combat head lice in kids. Its active ingredient, permethrin, has been used for years as a head lice treatment.

According to the American Academy of Pediatrics (AAP), NIX “is currently the recommended treatment for head lice, with retreatment in 7 to 10 days if live lice are seen.”

This is a controversial recommendation. As the prevalence of head lice increases in schoolchildren, it’s worth taking a closer look at whether this commonly used, “recommended” course of treatment makes any sense.

NIX doesn’t kill the eggs

The instructions say that you're to saturate the hair with the NIX lice treatment, leave on for ten minutes and rinse out. The permethrin is supposed to kill the live head lice (the crawling insects).

Then you’re instructed to do a thorough nit-combing, to remove all the nits. According to the CDC, "Permethrin kills live lice, but not unhatched eggs.” The eggs in their nits are unaffected by the NIX. The treatment is just to kill the mobile insects.

Some permethrin residue remains even after rinsing out the Nix. This residue may affect newly hatched lice for a few days after the initial treatment.

Lice hatching after that window remain unaffected.

The instructions say to re-treat after 7 days have passed, if live insects are spotted again. (This might happen if a couple of nits were not combed out, which later hatched, or if some of the insects survived treatment with the NIX.)

So … the reason NIX is recommended is simply to kill the live insects so that they aren’t transmitted to other people. (And presumably also because dead insects are easier to comb out than live ones.) You still have to do all the time-consuming and painstaking nit-combing. Fair enough.

But there are a couple of good reaons NOT to use NIX lice treatment to try to kill the live insects before combing out.

Head lice have developed resistance to NIX

Permethrin has been prescribed for head lice so much, for so many years, that head lice populations have developed resistance to this chemical. According to the CDC, “Treatment failures can be common, depending whether lice are resistant to permethrin in the patient’s geographic location.”

This trend is only increasing as permethrin continues to be heavily used all over the country. There’s no way to tell whether head lice on your child’s head will be susceptible to NIX. You can be sure, though, that resistance to the pesticide will continue to increase as long as it is overused.

Permethrin is a neurotoxin

I was surprised to learn how many safety concerns there are surrounding permethrin, given the widespread use of this pesticide on children. Here are some of the safety issues to consider:

Permethrin is a synthetic chemical that acts as a neurotoxin. It kills insects by damaging their nervous systems. It has complex effects on the nervous system in mammals. It's poisonous to dogs, and it can kill cats.

According to the Insecticide Fact Sheet from the Journal of Pesticide Reform, permethrin “is a neurotoxin. Symptoms include tremors, incoordination, elevated body temperature, increased aggressive behavior, and disruption of learning. Laboratory tests suggest that permethrin is more acutely toxic to children than to adults.”

The EPA has also classified permethrin as a likely human carcinogen (cancer-causing agent).

The official NIX website posts warnings that using their product may cause scalp irritation, eye irritation, breathing difficulty or asthmatic episodes. It cautions users not to leave the NIX on for more than ten minutes, and not to re-apply within seven days.

The CDC states that permethrin is not approved for use on children less than two years old. It’s hard to see why anyone would want to use it children or adults, given its limited efficacy, the probability of treatment failure, and safety concerns.

So if NIX lice treatment was the only treatment available for head lice, I still wouldn’t use it. I think it would be far better just to use a regular conditioner in conjunction with a good lice comb.

If you want something to kill the insects first, so you’re combing out dead lice rather than live ones, you can use an enzyme shampoo. The enzymes also loosen the nit glue, so that nits come out more easily.

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