Alternative Medicine Research Today is a free monthly online journal that collates and summarizes the latest research about Alternative Medicine, including details on complementary medicine, alternative therapies, homeopathy.

Lethality of essential oil constituents towards the human louse, Pediculus humanus, and its eggs.

Priestley CM, Burgess IF, Williamson EM

GlaxoSmithKline Nutritional Healthcare, Royal Forest Factory, Coleford, Gloucestershire, GL16 8JB, UK.

Essential oils have been widely used in traditional medicine for the eradication of lice, including head lice, but due to the variability of their constitution the effects may not be reproducible. In an attempt to assess the contribution of their component monoterpenoids, a range of common individual compounds were tested in in vitro toxicity model against both human lice (Pediculus humanus, an accepted model of head lice lethality) and their eggs, at different concentrations. No detailed study into the relative potencies of their constituent terpenoids has so far been published. Adult lice were observed for lack of response to stimuli over 3 h and the LT(50) calculated, and the percentage of eggs failing to hatch was used to generate ovicidal activity data. A ranking was compiled for adult lice and partially for eggs, enabling structure-activity relationships to be assessed for lethality to both, and showed that, for activity in both life-cycle stages, different structural criteria were required. (+)-Terpinen-4-ol was the most effective compound against adult lice, followed by other mono-oxygenated monocyclic compounds, whereas nerolidol was particularly lethal to eggs, but ineffective against adult lice.

Published 5 June 2006 in Fitoterapia, 77(4): 303-9.
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