What to try if you have lice

If you’re sure you’ve got lice, and they withstand a round or two of drugstore products, there are other approaches available. In one recent analysis, Consumer Reports suggests physically and repeatedly removing lice with a fine-toothed comb over the course of days and weeks until they are all gone.

For the lice-weary, prescription medicines approved by the Food and Drug Administration now include a lotion called Sklice, which was introduced in 2012 and interferes with a different part of the insect’s nervous system through an active ingredient called ivermectin that is produced by fermenting bacteria. Two days after treatment with Sklice, according to a 2012 study, 95% of people were lousefree. That dropped to 74% two weeks later. Natroba, which came out in 2011, attacks yet another area of the nervous system. No combing is necessary, and it claims to be 85% effective after two weeks.

A third prescription option is Ulfesia, which has been available since 2009 and is made with benzyl alcohol that suffocates the lice but doesn’t harm the eggs. There’s also an older drug called Ovide, made with malathion, which has long been used as a pesticide against all kinds of insects. But many lice are resistant to it. Some of these products require two applications. And some are only safe for kids over a certain age or size, making it worth talking to a doctor about the pros and cons, including the hefty price many products command. By keeping newer drugs locked behind prescription barriers, one hope is to avoid the kind of overuse that may have contributed to resistance against older treatments.

And if you are squeamish about the little critters, or you want to avoid drugs, there are any number of commercial agencies that will comb and check heads. Some even make house calls.

It turns out that doing nothing often gets rid of lice too, eventually. One possibility is that a course of antibiotics for an ear infection or some other illness extinguished the lice, which feed off of our blood and are often susceptible to the drugs. Or it might be that, even after years of being colonized, kids sometimes age out of lice.