Microbiological stability of cosmetics by using challenge test procedure

A cosmetic product is a substance or mixture intended to be applied on the outer surfaces of the human body or on teeth, on the mucous membranes of the mouth, with the purpose of cleaning, smelling, modifying, protecting, maintaining them in good condition. In order to prevent microbial proliferation in cosmetics, substances with antimicrobial activity are used, to inhibit the development of microorganisms. Among the most commonly used cosmetic contaminants, there are spore-forming bacteria, molds, yeasts and bacteria. In the following study through the challenge test, four cosmetics products were analyzed, including an ultra-moisturizing anti-aging facial cream, a biphasic tonic, an aqueous tanning gel and a hair wax. The main goal was to evaluate the conservative properties of products in catching any microbial contamination, that may occur as a result of use. The Challenge Test has proved to be useful and appropriate to predict the behavior of cosmetics in the event of bacterial contamination. Starting from a high microbial charge for all products, microbial growth after 7 days is stopped, thus demonstrating the good conservative properties of the analyzed products.