Anti-Influenza Virus Activities of Commercial Oregano oils and their Carriers

Commercial Oregano oils with high concentrations of carvacrol have been vigorously promoted as antiviral agents effective against colds and ‘flu, including the pandemic H1N1 virus. However there seems to be no evidence to support these claims. Furthermore, since carvacrol itself is known to be toxic, so-called “carrier oils”, such as olive oil, have been included in formulations to ameliorate the potential toxic effects. We compared the anti-influenza virus activity of several preparations, with and without “carriers”, and pure olive oil and carvacrol, by means of quantitative assays for H1N1 influenza virus, and for cytotoxicity in human lung epithelial cells. A range of concentrations was evaluated, including those relevant to consumer applications. All five Oregano oils showed significant antiviral activity, as did olive oil by itself, although their potencies were not comparable to a standardized preparation of Echinacea purpurea. Carvacrol was also very active, but it was also strongly cytotoxic. In addition all the Oregano oils were more cytotoxic than Echinacea purpurea. Thus certain commercial Oregano oils do possess anti-influenza virus activities, although these are less than a potent standardized Echinacea preparation, and furthermore the toxicity of the oils to lung epithelial cells, at doses relevant to consumer applications, is a limiting factor in their usefulness for oral applications.