Abstract

The preservative efficacy test is a test method that is used to evaluate microbiological product stability (preservative efficacy). The performance of such test is also part of the legal requirements to prove the adequate microbiological quality and product safety of cosmetic products. It must, however, be emphasised that the efficacy statement provided in such tests cannot be seen as a proof of microbiological product safety. Historical data show that attempts to improve the validity of the efficacy statement by changing the test method or the required death kinetics have been disappointing. This paper describes a method that can lead to an improved efficacy statement. The principle is to use the preservative efficacy test as part of the microbiological quality management (MQM) system in such way that data and knowledge gained from the system are used to adapt the test to the actual situation. Efficacy testing, as specified in ISO 11930, can be used as the basic test method. The exact test protocol, however, must be applied, the spectrum of test-microorganisms should be extended and subsequent repetitions of the test are needed in case of relevant changes (formula, raw materials, production process). In the event of specific problems, additional testing can be conducted (e.g., in-use tests, repetitive PET). The implementation of an MQM-system is a prerequisite for the success of this approach.