You may have heard about the strain of head lice that can’t be killed by over-the-counter medicine commonly recommended by schools and health care providers. The so-called super lice have cropped up in 25 states, according to research presented recently at a meeting of the American Chemical Society.
Over-the-counter lice medicines use pyrethroids, which are synthetic versions of a chemical found in chrysanthemums. Pyrethroids lock onto receptors in insect nervous systems, paralyzing the parasites and eventually killing them.
Over the years, some lice have evolved so that pyrethroids no longer connect neatly with the receptors, reducing the chemical’s ability to kill the insect.
Head lice are tiny crawling insects that live in the hair on your head. The lice feed on blood sucked from the scalp and they lay eggs — called nits — that firmly attach to the hair shafts.
The most common symptom of head lice is itchiness, especially on the back of the head and neck and near the ears. These are areas where lice are more likely to live. Intense scratching can break the skin of the scalp and can lead to open sores and infection. However, it may take as long as two to three weeks after a lice infestation for the itching to begin.
Head lice spread by direct head-to-head contact and by sharing items such as combs, brushes, scarves and hats with an infected person. Anyone can get head lice — it is not a sign that a person is unclean.
While head lice can be a concern — and super lice would be a super concern — there still are drugs that can take care of the blood-sucking parasites, says infectious disease specialist Richard Watkins, MD.
Ivermectin, for example, is a drug that can eliminate super lice. However, these drugs are available by prescription only.
The prescription drugs are powerful enough that one dose will take care of the problem, Dr. Watkins says.
“Ivermectins are very effective against super lice,” he says. “For this drug, one dose will kill them all.”
If you or your child has lice, there’s no way to know whether you’re dealing with the regular critters or the super strain until you try to treat them. If over-the-counter medicine, properly applied, doesn’t work, that’s when you know you or your child likely has super lice, Dr. Watkins says.
Make sure you follow the directions on the over-the-counter medicine. Many times, the treatments don’t work well because many people don’t use them as directed, Dr. Watkins says.
Often, people fail to apply a second treatment about a week later. This second treatment is necessary to kill the survivors of the first application. Or people often don’t keep the medicine on their scalp long enough to be effective.
“Most people don’t use over-the-counter medications properly,” Dr. Watkins says. “You have to leave them on overnight and then reapply it again five to seven days later.”
The best prevention is to not share combs, brushes, towels or hats with others and to avoid physical contact with someone who has lice.
It also helps to examine and treat all members of your household who have had contact with a person with lice. Also, tell the school, day care center or baby-sitter if your child has head lice. The other children can be checked and treated too, if necessary.
Call your health care provider if over-the-counter treatments fail to work or if there are signs of an infection, Dr. Watkins says. Signs of infection include:
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