Comparative in vitro tests on the efficacy and safety of 13 anti-head-lice products.

Head lice are an emerging social problem, not only in economically poor countries but also in practically all other societies. Several of the common anti-louse products have lost--at least in part--their efficacy due to increasing resistance of lice against insecticides such as permethrin or allethrin. Other compounds, like lindan, were redrawn or banned due to high toxicity. Some recently developed products are based on dimethicones or cyclomethicones and turned out to be easily inflammable. Other styled medicinal products are based on plant extracts-some were proven of high efficacy-others of ineffectivity. The present study investigated in in vitro tests the anti-head louse efficacy of 13 products, the contents of which are used worldwide: Aesculo-Gel L, EtoPril, Goldgeist Forte, InfectoPedicul, Jacutin Pedicul Fluid, K.Laus, Liberalice, Licatack, Mosquito Läuse-Shampoo, Nyda, Paranix, Picksan Louse Stop, and Wash Away Louse. It turned out that several of them are easily inflammable, and therefore, they endanger users (InfectoPedicul, Paranix, EtoPril, Nyda, Goldgeist Forte, and K.Laus, see Table 1). Others have to remain for many hours on the hair in order to reach efficacy (Table 4). During such long periods, highly dosed oils may become inhaled and thus may become dangerous for the user's lung epithelia by covering them. When incubating the lice for 3 or 10 min in vitro, only the following products killed all lice exposed to these products: InfectoPedicul, Paranix, Jacutin Pedicul Fluid, Nyda, K.Laus, Picksan Louse Stop, Licatack, and Wash Away Louse. When evaluating the possible dangers for the users, the last three products, especially, derived from plant extracts, are safe and highly effective at the same time. Furthermore, they had been tested dermatologically as "very good".