Natural products and their application to the control of head lice: An evidence-based review

Head lice are insects that have been parasitizing human beings for thousands of years. Chemical pediculicides have been used extensively for the treatment of infestations since the early 20 century. Resistance to these pediculicides, such as permethrin, is constantly increasing and there is a need for the development of new effective compounds killing adult lice and eggs. Natural products have been used in traditional medicine since long and have been more Correspondence/Reprint request: Dr. Jörg Heukelbach, Department of Community Health, School of Medicine Federal University of Ceará, Brazil Jörg Heukelbach et al. 2 and more the issue of interest, since the costs are usually lower and they are in general considered less toxic. However, toxicology information on natural products is poor. Here we present an evidence-based review on plant compounds for the treatment of head lice infestations. An overview is given on published evidence on the use of pediculicides and ovicides in in vitro studies and clinical trials to cure pediculosis. Additionally, the available data on deterrent compounds are reviewed. We conclude that large numbers of plant products, such as neem and tea tree oils, offer promise for new compounds to treat head lice infestation. The number of clinical studies is very limited, and there is an urgent need to increase research assessing the effectiveness and safety of promising compounds. Over the counter natural products should be supported by in vitro data and adequately designed controlled trials that evaluate cure rates and safety. Providing that a new family of synthetic insecticides is not discovered, it is possible that plant products will replace chemical insecticides on the market in future.