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Microbiological safety testing

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Legal demands for cosmetic products

Cosmetic products should be safe under normal or reasonably foreseeable conditions of use. The regulation on cosmetic products (EC 1223/2009) requires for the cosmetic product safety report the results of preservation challenge test to prove the microbiological safety.


The regulation itself didn’t specify the test procedure for the challenge test. Beside the test from the EU and US pharmacopoeia in-house test protocols are established since many years. The applicability of the schülke KoKo test for the evaluation of the microbiological safety of finished cosmetic products is assessed in the paper: Evaluation of the Microbiological Safety of Finished Cosmetic Products 

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) of the SCCS publication “Notes of Guidance for the Testing of Cosmetic Ingredients and their Safety Evaluation” is an obligation for carrying out a preservation test with all cosmetic products which could be contaminated under normal storage and usage conditions or if an infection risk for the consumer exists.

Period after opening « PAO »

The 7th Amendment to the Cosmetics Directive has introduced a new requirement on the labelling of cosmetic products. Products with a minimum durability of more than 30 months must indicate the period of time after opening for which the product can be used without any harm to the consumer.  


This information shall be indicated by the symbol and the period itself in months and/or years. For products with a minimum durability of more than 30 months, it is not allowed to indicate the minimum durability instead of the “Period after Opening”.  

A variety of relevant methods may be used to support the period indicated on a product, including those used during product development, since there is no officially sanctioned methodology that could be used. Examples of sources of information for assessing a product’s PaO may include:
• microbiological challenge tests
• stability data - analytical data (e.g. preservative analysis)
• type of packaging - experience with similar formulations and products
• consumer habits and practices

Source: Practical implementation of Article 6(1)(c) of the Cosmetics Directive (76/768/EEC) - LABELLING OF PRODUCT DURABILITY: “PERIOD OF TIME AFTER OPENING”

The schülke KoKo test

In this test, the schülke KoKo test, a mixture of bacteria, yeast and moulds are inoculated 6 times (once a week) into the test material (see graph), with the goal of keeping the test material germ free for this period.


The schülke KoKo testThe inoculum contains pathogenic microorganisms as gems which are well known for product spoilage. All species have to be cultivated separately and mixed directly before the addition, to ensure a constant composition and germ count of the inoculum. Its germ count is approximately 107-8 cfu/ml, which means a germ count of approximately 106 cfu/ml in the sample.
A sample can be called well preserved, if it passes a period of six weeks under the above described laboratory conditions without showing microbial growth on the test batches. That means even after the sixth inoculation no microbial growth can be observed. From many years of experience in the use of this test method these results can state the microbiological stability of 30 months which is recommended for cosmetic products.

ISO 11930

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« 


Compared to other methods ISO 11930 is an overall standard to evaluate the antimicrobial stabilisation of a cosmetic product. With the decision diagram in Annex A also formulations intrinsically hostile to microbial growth, specific manufacturing conditions, packaging and/or conditions for use and the reference to ISO 29261 (Guidelines for the risk assessment and identification of microbiologically low-risk products) are covered.

schülke prepared a comparison of ISO 11930 and different established methods in the market and run comparative tests for ISO 11930, Ph. Eur. 7 and the schülke KoKo Test.

Additional literature

Comparison of microbial challenge testing methods for cosmetics

Comparison of microbial challenge testing methods for cosmetics
H&PC Today | Vol. 8(2) | 3/4-2013

ISO 11930 – A Comparison to other Methods to Evaluate the Efficacy of Antimicrobial Preservation

ISO 11930 – A Comparison to other Methods to Evaluate the Efficacy of Antimicrobial Preservation
SÖFW-Journal | 138 | 7-2012

Evaluation of the Microbiological Safety of Finished Cosmetic Products

Evaluation of the Microbiological Safety of Finished Cosmetic Products

Period after opening « PAO »

Period after opening « PAO »
Presentation 10-2011