Challenge testing of preservation systems

Preservation efficacy testing, or challenge testing, has for many been a vital tool in judging a personal care product’s safety and is a requirement for EU market access. Here, evident ingredients explains why meta analysis is a powerful tool in understanding and predicting challenge test results

Preservation efficacy testing (PET), or challenge testing, has for many been a vital tool in judging a personal care product’s safety and is a requirement for EU market access. According to Regulation (EC) No 1223/2009, manufacturers are required to include the results of a PET in the Cosmetic Product Safety Report, though the exact method to be employed is not specified.

In practice, today most PETs in Europe are conducted according to the methodology laid down in the European Pharmacopoeia chapter 5.1.3, but tests according to ISO norm 11930 are becoming increasingly popular as well. For both tests the execution is similar: the cosmetic product is separately inoculated with five specified microorganisms, and the number of remaining colonies is determined at set points in time over the course of 28 days.

From the colony counts, logarithmic reduction factors of the initial microbial inoculation concentrations are calculated. These factors describe how quickly the preservation system was able to reduce the microbial contamination and are the basis for determining if the sample has achieved one of the passing grades (‘A’ or ‘B’) or failed the test

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