The challenge test is the gold standard method for verifying the actual effectiveness of a cosmetic product's preservative system. This test involves deliberately inoculating several types of microorganisms—bacteria, yeasts, and molds—directly into the formula. The product is then monitored for several weeks to assess the preservative's ability to eliminate these microorganisms or prevent their proliferation. The procedure is standardized and recognized by both European regulations (Regulation EC 1223/2009) and the Swiss Cosmetics Ordinance (OCos/OSAV), making it an essential test for marketing products in Switzerland and the European Union.
The challenge test replicates real-life conditions of use. Each time the bottle or jar is opened, small amounts of microorganisms from the fingers, the ambient air, or the environment of use can enter the formula. By simulating these repeated contaminations, the test verifies that the preservative system effectively protects the product against microbial growth.
During the observation period, samples are taken at regular intervals and analyzed microbiologically. If no multiplication is detected, the preservative is considered effective for the expected shelf life of the product. Conversely, the presence of colonies indicates that the preservative system is insufficient and requires reformulation or adjustment of the preservative concentration.
By confirming that microorganisms cannot grow throughout the shelf life, the challenge test guarantees that the product will remain healthy, stable, and safe even after several weeks or months of use. This proof of microbiological stability is an essential part of the safety file required for the constitution of the DIP/PIF. It is therefore essential for any marketing in Switzerland and Europe, ensuring compliance with regulatory requirements and consumer confidence.