EVALUATION OF THE PRESERVATIVE PROPERTIES OF THYMUS-VULGARIS ESSENTIAL OIL IN TOPICALLY APPLIED FORMULATIONS UNDER A CHALLENGE TEST

The preservative properties of thyme essential oil (3%) with a known c omposition were evaluated in two types of final formulations, suitable for use as pharmaceutical or cosmetic vehicles, by means of a standar d challenge test proposed by the latest European Pharmacopoeia, The re quired preservation efficacy criteria were satisfied against the bacte rial strains, against the yeast in one of the formulations, but not ag ainst the mould strain involved in this study, Interactions between th e essential oil compounds and other factors present in the final formu lation might have influenced the activity of this essential oil, leadi ng to an incomplete satisfaction of the criteria.