It is reasonable to wonder whether active antimicrobial ingredients such as preservatives and boosters of preservation may exert their function also against microbial cells inhabiting our skin, thus altering skin Microbiota composition. This experimental study, performed in cooperation with Complife laboratories and the University of Novara, investigates this topic on Phenoxyethanol and DMDM Hydantoin; the first is the most used Personal Care preservatives worldwide, the second is characterized by a completely different chemistry and mechanism of action. The study compares the antimicrobial efficacy of the two molecules -at same dosages- against standard microorganisms, generally used in Cosmetics (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Aspergiullus brasiliensis), and pools of microorganisms isolated from the face of 20 human healthy volunteers. In addition to this, the study made possible the investigation of skin face microbiota composition, confirming what is reported in literature: this skin site is mainly composed by gram positive bacteria, belonging to the staphylococcaceae family.
Results demonstrated how both molecules (Phenoxyethanol and DMDM hydanotin) are characterized by comparable antimicrobial efficacy versus standard cosmetic microorganism strains and face-skin isolated pools. Does this put the basis to consider the two preservatives as not anymore skin safe? No, it doesn’t; On the contrary, further studies are needed to evaluate the topic in object. First, because this experimental investigation did not enabled us to work on the entire human face microbiota, but only on the small portion of it that was able to grow in the adopted cultivation conditions. Second, it is possible to assume that bacterial behaviour towards the two chemicals would have been different if in-vivo treated. It is now in progress a new study that, starting from these preliminary results and conclusions, will evaluate the topic after an in-vivo treatment, followed by metagenomics analysis.