A Head Scratcher:
How to Get Rid
Of a Pesky Parasite

Lice are getting tougher.

In recent years in the U.S., head lice have been developing resistance to the insecticides in over-the-counter treatments such as Nix and RID. And while the most common prescription treatment, Ovide, remains effective in the U.S., medical studies in the United Kingdom show that bugs there have developed a resistance to the insecticide malathion, an active ingredient in Ovide.

A number of new treatments are in the pipeline, but are still a ways off from approval by the U.S. Food and Drug Administration. In the meantime, many people are searching for new ways to kill these pests -- which affect six million to 12 million people each year in the U.S., occurring in all areas of the country and across socioeconomic strata.

Resistant and susceptible lice are indistinguishable to the eye. But even in areas where resistant lice have been found, many experts say that over-the-counter treatments are good first options. They are inexpensive, at usually under $10 a package, and don't require a trip to the physician.

Bayer HealthCare, the maker of RID, says its product is effective when used as directed -- including combing out the hair between two applications of the shampoo. The company says it believes any problems with efficacy and reinfestation are linked to incorrect application.

Nit-picking services, where someone manually combs out the lice and their eggs, are another alternative that has been growing in popularity -- and some even make house calls, such as Lousey Nitpickers, which operates throughout Southern California.

It is difficult to say how widespread resistant lice have become, say public-health experts, but reports began appearing in medical journals in the late 1990s. Bugs that are resistant to permethrin and pyrethrins -- the agents in over-the-counter treatments -- have been found in many places, including parts of Florida, Massachusetts, Texas and California, according to John Clark, a professor of environmental toxicology and chemistry at the department of Veterinary and Animal Sciences at the University of Massachusetts, Amherst.

The development isn't surprising, since all insects exposed to pesticides will develop resistance over time. For example, mosquitoes developed a resistance to the pesticide DDT after years of sprayings. Richard Pollack, a research associate at the department of immunology and infectious diseases at Harvard University's School of Public Health, says that some lice have a natural ability to eliminate toxins from their bodies, which they pass on to a new generation.

Besides over-the-counter treatments and combing services, you can purchase a special lice-and-egg-removal comb at most drugstores and try combing out the pests at home. But experts warn that any combing treatment can be time-consuming. It can entail several hours of daily combing for about two weeks, says Craig Burkhart, a clinical professor of dermatology at the University of Toledo's College of Medicine, in Ohio.

A physician could also prescribe Ovide lotion, which contains malathion and costs about $100-$140. Health insurance may cover part of the costs. The other prescription option is the insecticide Lindane, though it remains controversial. Lindane shampoo and lotion, distributed by Alliant Pharmaceuticals, isn't available in California and carries a so-called black-box warning on its label regarding possible links to rare seizures and deaths.

There are also herbal remedies on the market with ingredients like tea tree oil, rosemary and lavender. But "there's a real absence of data showing that they work," says William Brogdon, a research entomologist with the Centers for Disease Control and Prevention. And "If they are not effective, you are wasting your money."