FRIDAY, Aug. 5 (HealthDay News) -- Combing wet hair with a fine-tooth comb is a more effective treatment for head lice than over-the-counter chemical products, a new British study finds.

The discovery is important because head lice are showing increasing resistance to over-the-counter treatments, according to the researchers.

Head lice are tiny, wingless insects that feed on small amounts of blood. And they are easily spread, particularly among children, through close contact and sharing personal items such as hats.

Common chemical head lice remedies such as Nix and malathion appear to be increasingly ineffective against head lice. Nix cured only 10 percent of head lice cases and malathion only 17 percent, the investigators found.

"Our study confirms that developing insecticide resistance in head lice to the main two actives used in pediculicides -- organophosphates and pyrethroids -- makes them very ineffective," said lead researcher Nigel Hill, the head science officer in the department of infectious and tropical diseases at the London School of Hygiene and Tropical Medicine.

"Whilst I feel many parents and health professionals already believed this to be the case, our study has shown just how low success rates with these products really are," he added.

The study results appear in the Aug. 4 online edition of the British Medical Journal.

In their study, Hill and his team compared chemical treatments with a product sold in Great Britain called the "Bug Buster kit." Each kit includes special combs that remove lice and nits, and the instructions call for using the combs along with hair conditioner while the hair is wet. Hair washing and combing is supposed to be done four times over a two-week period.

During the study, 126 children with head lice were assigned to treatment with the Bug Buster kit or the insecticide treatments. The researchers looked for head lice two to four days after the end of treatment.

Hill's team found that the Bug Buster kit was four times more effective in curing a head lice infestation than the chemical products. The cure rate for the kit was 57 percent, they reported.

"This is the first hard evidence that the methodical use of a well-designed fine-tooth comb in wet and conditioned hair can break the life cycle and effectively eradicate lice," Hill said. "So-called wet combing with conditioner has been widely advocated for several years as a treatment, but with no real evidence it worked. Our study shows clearly it is a viable alternative to current medicated treatments."

The researchers realize that the Bug Buster results aren't totally satisfactory. "Some may consider that the cure rate of only 57 percent we detected with the Bug Buster kit is still unacceptable and may not provide an efficient treatment against head lice," the authors wrote.

"We would like to see manufacturers of insecticidal compounds and formulators of pediculicidal products urgently address the need for novel actives to be registered for use against head lice," Hill said. "There are already candidate compounds which are likely to be 100 percent effective, and every effort should be made to bring these to market as soon as possible."

One expert believes the new study demonstrating the emergence of chemical-resistant head lice could foreshadow problems in the United States.

"There is a scary lesson to the American public in this study," said Dr. Dale Lawrence Pearlman, of Family Dermatology in Menlo Park, Calif., and inventor of a nontoxic head lice treatment, called Nuvo.

"The study concludes that in a country like England, which has extensively used nerve poison-based stuff, you're going to produce a population of head lice that are mean, ornery and not killable with nerve poisons," he said.

Pearlman noted that in the United States, Nix is already considered unreliable for treating head lice. Malathion, which has just been released for use in the United States, may also breed resistant head lice like those seen in the British study.

"Their result with Bug Busting suggests that you can cure about half the kids," Pearlman said. "That's a disappointing number. In addition, what happens two months later? It means that they can get re-infested by the kids that Bug Buster didn't cure."

Pearlman believes the answer to head lice lies in the development of nontoxic approaches that the lice cannot become resistant to.

"There is also the very scary scenario that parents can expect that the more neurotoxic products are used in America, the more we are going to have a problem of resistance like the British," Pearlman said.

More information

The National Pediculosis Association can tell you more about head lice.