Background: An estimated 6 to 12 million cases of head lice infestation occur in the United States annually. This number is rising because of the increasing resistance of lice to chemical shampoos. Other treatments include louse combs and home remedies of unproven effectiveness. A new treatment uses hot air to kill lice. Several studies have shown that body lice and eggs are desiccated in as little as five minutes after exposure to air that is 122° to 131° F (50° to 55° C). Goates and colleagues studied several methods of delivering hot air to determine if hot air treatment is an effective pediculicide.
The Study: Schoolchildren older than six years with head lice were included in the study. Live lice and eggs were combed out and collected from one side of each child's head until no more were forthcoming. The children's scalps were then treated with one of six different hot air treatments, after which live lice and eggs were combed out on the second side of each child's head.
The six hot air treatments were a bonnet-style method, two handheld hair dryer methods, a modification of a wall-mounted dryer, and two “Lousebuster” methods (a custom-built, high-volume dryer developed by the authors). Most approaches, other than the bonnet-style, treated the hair section by section. One Lousebuster method used a comb-like handpiece to “rake” the hair to expose the hair roots to hot air. All methods took about 30 minutes to complete, and temperatures were tailored to the patient's comfort.
Specimens from both sides of the children's hair were compared after two weeks of incubation using microscopic examination to determine relative percentages of dead lice and nonhatching eggs. A follow-up examination and treatment with the most effective of the six treatments (i.e., Lousebuster with handpiece) was performed on select patients with a high probability of reinfestation.
Results: In the study, 169 children underwent hot air treatment; most were girls, and the median age was 10 years. All hot air treatments had higher louse eradication rates and lower egg-hatch rates than no treatment (see accompanying table). At follow-up one week after treatment, 10 out of 11 patients treated with a Lousebuster with handpiece had no lice.
|Method||Number of patients||Increase in louse eradication rate (%)*||Decrease in egg hatch rate (%)*|
|Bonnet-style hair dryer||54||7.3||19.2|
|Handheld hair dryer (diffuse heat)||26||8.9 (not significant)||45.4|
|Handheld hair dryer (direct heat)||27||44.7||42.2|
|Lousebuster† with comb-like handpiece||18||72.3||44.9|
Conclusion: The authors conclude that hot air treatments at temperatures lower than blow-dryers effectively treat head lice, but no method results in 100 percent louse mortality. The bonnet-style method appears to be least effective, and the authors do not recommend it. The Lousebuster with handpiece appears to have the highest kill rate.