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Comparison of Microbial Challenge Testing Methods for Cosmetics

Schülke & Mayr GmbH
Special Additives International, Robert-Koch Str. 2, 22851 Norderstedt, Germany


The microbial safety of cosmetic products is an important consideration. The results of preservation challenge test are required for the safety assessment. Different methods are commonly available and used in the cosmetic industry. These methods are different in the type of microorganisms used, the inoculation of samples, the criteria of acceptance, and the consideration of preservative stability. They will be compared by applying them on a Q 10 containing body lotion. Using borderline concentrations of the preservative system shows how different criteria of acceptance lead to different assessments.
However, in order to fix the period after opening (PAO) additional data beside the microbiological challenge test have to be considered.


Cosmetic products should be safe under normal or reasonably foreseeable conditions of use. While the regulation on cosmetic products (EC 1223/2009) (1) requires that the cosmetic product safety report demonstrates the results of preservation challenge test to prove the microbiological stability, it does not specify the test procedure for the challenge test. Alongside the test from the EU (2) and US pharmacopoeia (3), the Personal Care Products Council (4), the ASEAN Cosmetics Association (5), in-house test protocols (6, 7) have been established for many years. A new method, the first edition of ISO 11930 was published in April 2012 under the title “Cosmetics - Microbiology - Evaluation of the antimicrobial protection of a cosmetic product” (8). This paper will examine the comparability of these methods.

Demands for challenge testing are specified only in the SCCS notes of guidance . In paragraph 4-4 “Guidelines on Microbiological of the Finished Cosmetic Product“ in the 8th revision (December 2012) (9) of the SCCS publication “Notes of Guidance for the Testing of Cosmetic Ingredients and ...

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