MSL Solution Providers - Preservative Efficacy Testing (PET)

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Preservative Efficacy Testing (PET)

Preservative Efficacy Testing (Challenge) is the process of testing the effectiveness of the preservative system in cosmetic products. The EU Cosmetic Regulation does not define a specific test method to be used for satisfying the requirement for microbiological robustness; it leaves the choice of an appropriate test method up to the Responsible Person. Challenge testing is a requirement for products where the formula is not regarded as microbiologically low risk e.g. >20% alcohol. Results of a challenge test or justification for bypassing a challenge test must be reviewed in the Cosmetic Product Safety Report. The following test protocols are all valid Preservative Efficacy Testing (PET) methods from around the world and can all be undertaken by MSL. MSL’s preferred test method is EN ISO 11930 which is deemed to be the most appropriate for supporting EU cosmetic regulatory assessments.

  • ISO 11930 – Specifically aimed towards cosmetic products, it consists of 3 test time points, 5 organisms are used in a separate 1% inoculum spikes at day 0. Used in conjunction with ISO 29621.
  • Risk assessment (ISO 29621) – referenced in ISO 11930, gives guidance when determining if a product is low risk based on information ranging from packaging properties to a products chemical properties.
  • EU Pharmacopeia – This method can be applied to cosmetic products intended for the European market however it is primarily aimed at medical products. It consists of 4 test time points, 4 organisms are used in separate 1% inoculum spikes at day 0.
  • US Pharma – This method can be applied to cosmetic products intended for the US market however it is primarily aimed at medical products. It consists of 2 test time points, 4 organisms are used in separate 1% inoculum spikes at day 0.
  • Japanese Pharma – This method can be applied to cosmetic products intended for the Japanese market however it is primarily aimed at medical products. It consists of 2 test time points, 4 organisms are used in separate 1% inoculum spikes at day 0.
  • KOKO – Developed to test both preservative efficacy as well as preservative stability, a test sample is spiked 6 times at 1 week intervals and tested before each spike. Spikes quantities make up 4% of the original sample volume. This is a stringent test as samples must achieve less than 2log growth throughout the entire test.
  • Reduced – This is an in-house test MSL uses as indication test as to whether samples are classed as hostile to microorganism. The data gathered from this can be used in conjunction with ISO 29621 to determine the outcome of a risk assessment. With a reduced turn-around time of 10 days, this test is useful for formulators to decide if a product is ready to undergo a full test and results are available after 10 days.
  • Petra – This method is developed to give an indication as to whether a sample would pass a full preservative efficacy test. The sample is spiked at 2 time points with a 1% spike for 5 separate organisms and then tested 48 hours after. With a reduced turn-around time of 10 days this test is useful for formulators to decide if a product is ready to undergo a full test as it is quicker and cheaper than a full challenge.
  • Client-specific – MSL has extensive experience in adapting Preservative Efficacy Testing to suit a client’s specific requirements as well as providing guidance when deciding which test is appropriate for a specific product.

By using our in-house laboratory alongside our Responsible Person and Cosmetic Product Safety Report service you can save time and money. Running the Preservative Efficacy Test alongside the CPSR the process can be sped up significantly allowing you to get your products onto the EU market quicker.