Efficacy due to alcohol or something else in the mouthwash composition? Dirk Lachenmeier, CVUA Karlsruhe 27 March 2012 As it was previously noted, a considerable industry bias in mouthwash-related research exists . Therefore, it would be interesting to know the sponsor of the study and if the sponsor was affiliated with any of the mouthwash brands under investigation. To provide insight into the transferability of the results, data about the composition of the two mouthwash types under investigation would be important as the composition is highly variable between brands and types [2,3]. Did the two products have the same content of essential oils? What kinds of essential oils, which may have different efficacy dependent on type, were used? At least the manufacturer of the alcohol-containing products provides different product types with different composition, which one was it? Would it not have been a better experimental design to use the same formulation with and without alcohol than to use two commercial types of mouthwash, which may have additional differences other than the alcohol content? How can the conclusion that the difference is due to alcohol uphold, when the composition has not been characterized at all?  Lachenmeier DW: Safety evaluation of topical applications of ethanol on the skin and inside the oral cavity. J Occup Med Toxicol 2008, 3:26. http://www.occup-med.com/content/3/1/26  Lachenmeier DW, Keck-Wilhelm A, Sauermann A, Mildau G: Safety assessment of alcohol-containing mouthwashes and oral rinses. SOFW J 2008, 134:70-78.  Lachenmeier DW, Gumbel-Mako S, Sohnius EM, Keck-Wilhelm A, Kratz E, Mildau G: Salivary acetaldehyde increase due to alcohol-containing mouthwash use: a risk factor for oral cancer. Int J Cancer 2009, 125:730-735. Competing interests None declared.