How can we ensure that a cosmetic product remains stable against microbiological influences?
Preservation challenge tests represent a fundamental building block for evaluating the microbiological safety of cosmetic products. The test is intended to confirm that the cosmetic product prevents germ multiplication when used as intended and is therefore microbiologically stable.
The ISO 11930 standard on preservative challenge tests for cosmetics is in place since 2012. Whereas in the past the specifications of the European or American Pharmacopoeia were used as a guide, ISO 11930 now contains specifications for the performance and evaluation of stress tests that are specifically geared to the cosmetics industry.
What is the principle of the stress tests?
At the beginning of the challenge test, a cosmetic product is inoculated with 5 microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Candida albicans and Aspergillus brasiliensis). The initial bacterial counts are determined and the inoculated products are stored under defined conditions.
After defined time points (7 days, 14 days and 28 days), the bacterial counts of the inoculated products are determined in order to follow the development of the bacterial counts over the test period. Finally, it is checked whether the bacterial counts are reduced according to the specifications. This provides an indication of the microbial stability of the cosmetic product, since in many cases microorganisms can be expected to enter the product after it has been opened.
Regulation ISO 11930 specifies requirements for the reduction of microbial counts in the context of preservation challenge tests. These requirements are represented by means of logarithmic reduction values. According to the standard, if criterion A is met, it can be assumed that the product is protected from microbial proliferation. If only criterion B is achieved, further safety measures such as protective packaging must be taken to reduce the microbial risk during use accordingly and meet the requirements of the standard.
The cosmetics laboratories of the Tentamus Group analyse your products with regard to their microbiological safety, among other things, and carry out preservation challenge tests. In this way, you can ensure that the microbial risk to your customers during use is reduced and that the product complies with the standards.
Further information can be found here: Cosmetic Testing
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