The Essential oils (EO) are composed by a wide diversity of products. Therefore, their antimicrobial activity will be related to their composition, configuration, amount and their possible interaction. The traditional formulation containing EO (T-EO) is a complex mixture of phenolic compounds combined with determinate EO: 0.092% of eucalyptol, 0.064% of thymol, 0.06% of methyl-salicylate and y 0.042% of menthol. All of this solved in a hydroalcoholic vehicle containing from a 21.6% to a 26.9% of alcohol. Thus, T-EO contain ethanol, which is a chemical compound used in order to dissolve and stabilize the numerous substances present in the rinse. The concentration of ethanol present in the T-EO rinses, as previously said, is more than 20%. This concentration of ethanol, higher than 20%, is been found sufficient to dissolve the EO but insufficient to have a direct antibacterial effect. In fact, the manufacturer presents the alcohol contain (21.6%), among others, as an inactive ingredient in its formula. Over the years, the adequacy of the use of ethanol in mouthwashes, as well as their effects on the surfaces of composite restorations and their possible role in development of oropharyngeal cancer have been discussed. Although a direct cause-and-effect correlation between the development of oropharyngeal carcinoma and the use of alcohol-based rinses has not been demonstrated and probably it will never be (at least by epidemiological studies), it is considered desirable to eliminate ethanol from daily mouthwashes, especially for those patients at higher risk. Furthermore, the fact that the alcohol is present in its formula, have produced that some clinical practitioners do not prescribe the traditional formula due to the controversy of the issue. All this have lead to the development of new, alcohol free formulations of EO (Af-EO).