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Mar 24, 2026 - Cosmetics

Are preservative efficacy tests transferable?

In March, a new specialist article by the DGK working group “Microbiology and Operational Hygiene” was published, currently led by Joelle Nussbaum (BAV Institute). The article addresses a practical topic: the transferability of preservation challenge tests (PCT) in cosmetic products.

PCTs are a central component for testing the effectiveness of preservation systems, especially in water-based formulations. The execution is usually done according to ISO 11930, alternatively, methods from the European Pharmacopoeia (Ph. Eur.) or the US Pharmacopoeia (USP) can also be applied.

Given the high time and cost associated, many manufacturers ask whether existing test results can be transferred to slightly changed formulations. As a general rule: transferability must always be checked on a case-by-case basis. This requires careful evaluation of all available product data and a comparison with the new formulation.

Under certain conditions, an analogy test can be useful, for example with:

Changes in dyes
Adjustments to the perfume concentration
Increase in alcohol content
PCT results, however, cannot be transferred in cases such as:

Change of preservation system
Reduction of preservative concentration
Increase in water content
Change in water quality
The complete article offers detailed insights and practical recommendations on this matter.

You can view the publication at the following links:
https://tripicchio.scnem.com/a.php?sid=jqhq.1estas8,f=1,n=jqhq.1estas8,online
https://dgk-ev.de/publikationen/#mikrobiologie

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