Doubts surrounding the potential adverse effects of antimicrobial preservatives have modified the demand of consumers, who increasingly insist on the production of low-level and even preservativefree cosmetics. Protection of the product against microbial contamination is therefore focused on the packaging. This has prompted the emergence of a highly diverse array of so-called "protective", "overprotective", and "barrier" packaging. However, these designations are not normalized and the choice of the right packaging adapted to each cosmetic product is still essentially empirical, hazardous, and time consuming. The Cosmetic Valleys cluster has launched a commission to define a complete and experimentally-validated method to classify the level of protection of cosmetic packaging against microbial contamination. As reported herein, this required the development a specific bacteriostatic medium that can be used for seven days and an in vitro procedure that reproduces in-use contamination and consumer practices. Based on tests performed on over 800 packages of different origin and performance characteristics, we propose a classification, divided into six grades, to differentiate the protective efficiency of cosmetic packaging. This work can be considered as a first step towards a regulatory text. DeclarationsEthics approval and consent to participate. Not applicable, this study did not involve a clinical trial. Acknowledgements. The authors would like to thank GDR CNRS 3711 Cosm'Actifs and the CosmeticValley world cluster for their key role in promoting research in cosmetic sciences. We thank A.Edelman & Associates for efficient English reviewing. ReferencesANSM, Agence National de Sécurité du Médicament et des Produits de Santé (2012) Concentration de phénoxyéthanol dans les produits cosmétiques -Point d'information. https://ansm.sante.fr/Sinformer/Points-d-information-Points-d-information/Concentration-de-phenoxyethanol-dans-lesproduits-cosmetiques-Point-d-information Bossis E, Lemanceau P, Latour X, Gardan L. The taxonomy of Pseudomonas fluorescens and Pseudomonas putida: current status and need for revision. Agronomie 20 (1):51-63 Briasco B, Capra P, Cozzi AC, Mannucci B, Perugini P (2016) Packaging evaluation approach to improve cosmetic product safety. Cosmetics 3(3): 32 Crozier A (2018a) Chapitre 14 : Efficacité protectrice microbiologique des packagings. In « Evaluation des Produits Cosmétiques : La Sécurité » M. Feuilloley N. Orange Eds. Cosmetic Valley. Chartres, France.

The doubt regarding adverse effects of antimicrobial preservative, has modified the demand by the consumers which impose more and more the production of low-level and even preservative free cosmetics. In these products, protection against microbial contamination is therefore devoted to the packaging. This have prompted the emergence of a great diversity of so called “protective”, “overprotective” and “barrier” packaging, but this designation is not normalized and the choice of the right packaging adapted to each cosmetic product remains essentially empirical, hazardous and time consuming. The cluster Cosmetic Valleys decided to launch a commission aimed at defining a complete and experimentally validated method allowing to classify the microbiological protection level of cosmetic packaging. As reported herein, this was requiring the development a specific bacteriostatic medium usable over 7 days and an in vitro procedure reproducing in-use contamination and consumer gesture. On the basis of tests realized over 800 packs of different origins and performances, a classification in six grades was proposed in order to distinguish the protective efficiency of cosmetic packaging. This work can be considered is a first step towards a regulatory text.

Doubts surrounding the potential adverse effects of antimicrobial preservatives have modified the demand of consumers, who increasingly insist on the production of low-level and even preservative-free cosmetics. Protection of the product against microbial contamination is therefore focused on the packaging. This has prompted the emergence of a highly diverse array of so-called “protective”, “overprotective”, and “barrier” packaging. However, these designations are not normalized and the choice of the right packaging adapted to each cosmetic product is still essentially empirical, hazardous, and time consuming. The Cosmetic Valleys cluster has launched a commission to define a complete and experimentally-validated method to classify the level of protection of cosmetic packaging against microbial contamination. As reported herein, this required the development a specific bacteriostatic medium that can be used for seven days and an in vitro procedure that reproduces in-use contamination and consumer practices. Based on tests performed on over 800 packages of different origin and performance characteristics, we propose a classification, divided into six grades, to differentiate the protective efficiency of cosmetic packaging. This work can be considered as a first step towards a regulatory text.