A Revolution in Head Lice Treatment - It's a Lot of Hot Air! A major study reported in this month’s issue of the journal Pediatrics contends there is a better way than chemical shampoos to control infestations of head lice in children. To prove their point, researchers from the Department of Biology at the University of Utah in Salt Lake City describe their experiences with the use of 30 minutes of hot air, directed at lice-infested heads from a hair dryer or from a simple device developed specifically for the purpose. The researchers tested six different treatment methods—a bonnet-style hair dryer, handheld blow dryers with both diffuse and directed heating, a wall-mounted dryer of the type found in public restrooms, and two applications of a custom-built device called the LouseBuster, which the researchers describe as “an institutionally based machine that can be operated by health care providers, school administrators, or trained parents and other volunteers.” All of the methods had high egg mortality (more than 88 percent) but varied in their ability to kill hatched lice. The most successful—the LouseBuster—resulted in nearly 100 percent mortality of eggs and 80 percent mortality of hatched lice. The experiments were conducted on 169 elementary-school children who had infestations ranging in size from a few lice to hundreds. Researchers carefully combed one side of each subject’s scalp until all living lice and eggs were removed, and then treated the entire scalp with hot air at temperatures the children found comfortable. After treatment, the other side of the scalp was combed for the same amount of time. Lice and eggs collected from both sides were brought to the laboratory within three hours of removal, and examined under a dissecting microscope. The researchers checked dead lice for up to 18 hours to watch for the “resurrection effect” that sometimes occurs when lice seem to have been killed with pediculicides but are not really dead. “This was never a problem: all of our dead lice remained that way,” the researchers commented. The mechanism by which hot air kills lice is uncertain, the researchers said, but they believe desiccation is the most likely candidate. “Lice are highly susceptible to desiccation because their small size and flattened shape give then a high surface area/volume ratio.” They hope to determine the “exact proximal effect” of hot air on lice in the future, but in the meantime, they note that hot air treatments take just 30 minutes, compared with chemical shampoos or suffocation-based pediculicides, which require at least two and often three treatments a week apart. And it’s not likely that lice will become resistant to hot air, as they have to some chemicals, because that would require fundamental changes in their water physiology. “In summary,” the researchers said, “hot air is a significant improvement over other therapies used to treat head lice.” While hot air, however applied, seemed to kill both lice and eggs, researchers found the specially designed LouseBuster to be the most effective method. To more rigorously test the device, they treated 11 subjects without preliminary combing, to see whether the method could eradicate entire infestations of head lice. “None of the 11 subjects indicated that the treatment was uncomfortably hot, and none asked to stop treatment. At the one-week follow-up, 10 (91 percent) of the 11 had no lice. The eleventh subject had a single live male louse, which is not a viable breeding population.” The “LouseBuster” referred to in the report is described as “a custom-built, high-volume, hot-air blower with a molded hand piece that supports coarse teeth. The hand piece is pulled through the hair slowly while hot air blows opposite the direction of pulling. The combination of high temperature, high air flow, and the mechanical lifting of the hair leads to 98 percent of mortality of louse eggs and 80 percent mortality of hatched lice.” The description concludes that these mortality rates are sufficient to cure most subjects of head lice. The article, “An Effective Nonchemical Treatment for Head Lice: A Lot of Hot Air,” appears in the December 2006 issue of the journal Pediatrics. Correspondence should be addressed to clayton@biology.utah.edu. See also: |
