PARENTS battling infestations of lice on their children's heads will soon have a new weapon. A shampoo developed in the US causes lice eggs, or nits, to glow under ultraviolet light, making them much easier to spot and remove by hand.
Sydney Spiesel, a pediatrics professor at Yale University School of Medicine, formulated the shampoo after he was forced to manually remove pesticide-resistant lice and their eggs from a child's head. "The child had thick, blonde hair. It took me an hour to go through this kid's head," he says.
Every year about 14 million children get head lice in the US alone. For years, shampoos containing permethrin were used to keep the bugs at bay. But recent studies-and experience in schools and day nurseries-show that lice have become resistant to this and other common pesticides.
Another ingredient in some head-lice shampoos is lindane, which is approved by the Food and Drug Administration for treating lice. But lindane is a carcinogen, and the US Consumers Union and other groups have warned that it shouldn't be used on children.
This leaves parents literally nit-picking, using special fine-toothed combs bought at pharmacies. But the tiny eggs, at less than a millimetre across, are hard to see-and they stick tenaciously to the hair. If even a few eggs are missed, the child can quickly become re-infested. Knowing that lice eggs contain chitin-the polysaccharide from which the exoskeletons of arthropods are made-Spiesel took a commercial organic dye he knew would bind to chitin and added it to an over-the-counter shampoo. The dye is "delightfully cheap and delightfully non-toxic," he says.
The dye bound to the chitin in the eggs, but not to the hair or scalp. When Spiesel shone a "black" (UV) light on the eggs he saw a "brilliant glow" which made them easy to remove. Spiesel claims he now holds a patent on his lice-detecting shampoo, but he hasn't licensed it. He says he's looking for a business partner to help him bring it to market.
A non-profit group that discourages the use of chemical treatments says Spiesel's idea is too complicated. "We're not really excited by this idea. The best way is not to get people into dark rooms with black lights. We want to enable people to screen them routinely," says Deborah Altschuler, president of the National Pediculosis Association (www.headlice.org) in Newton, Massachusetts.
The association recommends that parents routinely check their children for signs of head lice and use a nit comb to remove eggs.
Author: Kurt Kleiner, Toronto
New Scientist issue: 24th June 2000
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