Microbial study of cosmetic products during their use by consumers: health risk and efficacy of preservative systems

To evaluate the microbial contamination of 91 cosmetics (23 o/w emulsions, 47 tensiolytes, 21 aqueous pastes) in three different states of use (intact, in-use, ending product) and the protection efficacy of the preservative systems most frequently used in the analysed cosmetic formulations. Methods and Results: Total bacterial count, isolation and identification of pathogenic isolates were performed on the collected cosmetics. About 10Æ6% of tensiolytes (13Æ5% bath foam, 6Æ7% shampoo, 10% liquid soaps) were contaminated by Staphylococcus warneri, Staphylococcus epidermidis and Pseudomonas putida. The efficacy of the preservative systems of two cosmetic products, tested against standard micro-organisms (Staphylococcus aureus ATCC 4338 and Pseudomonas aeruginosa ATCC 9027) and two isolates from cosmetics in this study (S. epidermidis and P. putida), satisfied the Cosmetics, Toiletries, and Fragrance Association and Official Italian Pharmacopeia criteria, while only one tested cosmetic respected the Rapid Challenge Test criterion. Conclusions: Contaminated cosmetic products are relatively uncommon, but some products, unable to suppress the growth of several micro-organisms, represent a potential health hazard. Significance and Impact of the Study: The challenge test may be performed not only during the preparation of the preservative system in the intact cosmetics, but also be used to evaluate the protection efficacy during their use.