October, 2010. My mother, at the tail end of a week babysitting my four kids, drops a text bombshell into my final kid-free airport reverie. School called kids have lice getting stuff when will you be here?
One moment, my husband and I were biking in France on our first trip alone in years. The next, I was standing in the bathroom picking bugs out of our daughter’s hair while my husband sat on the lid of the toilet, our son at his knees, peering at the boy’s scalp with a headlamp. My mother had bought Nix; we diligently followed the instructions on the box.
We figured that would be it. It wasn’t. A few weeks later, the lice were back and so were we, doing the same drill with a different box. October was Nix. November: Licefreeee. (Or so we thought.) December: RID and the electric “Robi” comb, which claims to “detect and destroy” lice on contact. January brought still more lice, skipping among our four children’s heads and mine like six-legged swingers, and a return to RID. In February, we tried a representative of the Lice Doctor. After March’s pulling-out-all-the-stops prescription-only malathion treatment, we were sure we had finally won, and so let our guard down in April, only to find in May that the lice had returned in full force.
Decades ago, Nix and I had cleared my mom (a teacher) of an infestation in a single evening. There was only one rational conclusion to draw. These were not my mother’s lice.
Today’s lice are tougher. Their exoskeletons are thicker. They hatch and mature on different schedules than they used to, wreaking havoc on established treatment directions. They have grown so resistant to Nix and RID that after only a minimum of Internet research I felt like a fool for bothering with either. Despite the increasingly desperate measures of defeated parents across the country, lice can’t be “suffocated,” either—the theory behind common home-remedy efforts to douse heads with olive oil, mayonnaise, or conditioner—but then, they never could (as rigorous testing, reported in the Journal of Pediatric Nursing, showed).
As for malathion lotion, the last-ditch prescription that our pediatrician’s office gave me after a series of tearful phone calls, and then only in extremely limited quantities? The pediatrician said it would work. The box said it would work. The package insert said that after seven days, 114 of 126 people were free of lice.
I was in the company of the other 12. My husband and I had shouting matches. The malathion had to work, he insisted: I still itched because it takes a while for the itching to go away. Because I had dandruff. Because I was crazy.
I wasn’t crazy, though, and I had the bugs on my comb to prove it.
While we attacked the lice with an old-school prescription, Lindane, that my sympathetic Peace Corps-vet pediatrician swore by, I started calling experts. Why hadn’t anything—including the malathion lotion—rid us of our scourge?
John Clark, professor of Environmental Toxicology at the University of Massachusetts, knows his lice. This is a man who keeps a colony alive on what’s essentially a giant fake human head, and he wasn’t surprised by our malathion fail. Some lice have a genetic mutation that leaves them immune to malathion, he said when we chatted; in Israel, the U.K., Denmark, and for that matter pretty much everywhere outside the United States, natural selection has long since favored lice with this resistance. The malathion lotion sold in the United States is slightly different than that used in other countries, however, and so far this has proved to be a saving grace: Three of the “inactive” ingredients intended to improve the smell of the American formulation turn out to also kill lice, as does the 78 percent isopropyl alcohol that makes up the rest of the bottle.
When the American malathion formulation was last tested in 2005, it proved effective against even otherwise malathion-resistant lice strains, but some experts believe that its days, too, are numbered. “When we looked at the formula,” Clark said, “it was clearly the isopropanol [another term for isopropyl alcohol] that was killing the lice. It wasn’t malathion or all these other compounds.” Ah, you say, but if isopropyl alcohol is so great, why not just pour a bottle of it over the child’s head? Here’s the problem. Any formulation that is designed to kill lice—RID, Nix, malathion, you name it—is also designed to leave a residue on hair after it’s been washed. This residue is supposed to be potent enough to kill those lice that don’t hatch until some days after the initial treatment. Isopropyl alcohol, however, doesn’t stick around. Once you wash it off, its work is through. Any surviving or newly hatched lice are left only with the malathion residue, and we’re left with the original problem: Malathion doesn’t kill all lice.