Microbiological testing is one part of understanding how a cosmetic or personal care product performs as it moves through development and towards commercial manufacturing.
Depending on the product, testing may include bacterial, yeast and mould testing and preservative efficacy testing. These tests provide information that can help the development and quality teams assess the formulation and determine whether further work may be required.
For brands, the important thing is understanding what testing is relevant to the individual product and allowing for it within the development process.
Why Is Microbiological Testing Important?
Cosmetic products can be exposed to microorganisms through ingredients, manufacturing, packaging and use.
The microbiological considerations will vary depending on the formulation. Water-containing products such as creams, lotions, cleansers and serums may require different considerations from products with a lower microbiological risk.
Testing gives the development and quality teams information about the microbiological condition of the product and, where relevant, how its preservative system performs.
The appropriate testing program should be considered for the individual formulation rather than applying the same approach to every cosmetic product.
What Types of Microbiological Testing May Be Used?
Two common areas of microbiological testing during cosmetic product development are:
- Bacterial, yeast and mould testing
- Preservative efficacy testing
The testing required will depend on the formulation, intended use and other product requirements.
Bacterial, Yeast and Mould Testing
Bacterial, yeast and mould testing provides information about the microorganisms present in a product sample at the time of testing.
Results can be assessed against the specifications or requirements that apply to the product.
For brands, this testing forms part of the wider quality picture alongside formulation development, stability testing and manufacturing controls.
The exact method and acceptance criteria will depend on the product.
Preservative Efficacy Testing
Preservative efficacy testing, sometimes referred to as PET or challenge testing, is used to assess how the preservative system within a formulation performs when challenged with specified microorganisms.
The test is carried out over a defined period, with results assessed at scheduled intervals.
If the formulation does not meet the applicable acceptance criteria, further development work may be required before the product progresses.
This could involve reviewing the formulation and preservative system before testing again.
Does Every Cosmetic Product Need the Same Testing?
No. The microbiological risk of a product depends on factors such as its formulation, how it will be used and the environment in which microorganisms may be able to grow.
A water-based cream, for example, may have different requirements from a product that presents a lower microbiological risk.
The testing pathway should therefore be developed around the individual product.
For brands that are new to manufacturing, this is an important distinction. A standard list of tests should not simply be applied to every formulation without considering whether those tests are relevant.
How Does Preservative Efficacy Testing Fit Into Product Development?
Preservative efficacy testing is generally considered once the formulation has reached an appropriate stage of development.
The purpose is to provide information about the performance of the preservative system within the finished formulation.
If the results indicate that the formulation needs further work, the development team can review the product before it moves further through the manufacturing process.
Allowing time for this within the development plan is important, particularly if further formulation work and repeat testing are required.
What About Microbiological Limits?
Cosmetic microbiological standards can set limits for the number of microorganisms present in finished products and may also include requirements relating to specified microorganisms.
The requirements can vary depending on factors such as the product category and intended area of use.
Rather than expecting brands to determine these limits themselves, the appropriate testing method and specifications should be established based on the individual product and its requirements.
Recognised Microbiological Testing Methods
Cosmetic microbiological testing may use recognised methods and standards depending on the product and testing requirements.
These can include standards relating to:
- Evaluation of preservative efficacy
- Microbiological limits
- Enumeration of bacteria, yeast and mould
- Detection of specified microorganisms
For example, ISO 11930 provides a recognised approach for evaluating the antimicrobial protection of cosmetic products, while ISO 17516 addresses microbiological limits for cosmetics.
The appropriate method should be selected according to the product and purpose of the testing.
Microbiological Testing at Delta
At Delta, microbiological testing is considered as part of the wider product development and manufacturing process.
The testing program will depend on the product and stage of development and may include:
- Bacterial, yeast and mould testing
- Preservative efficacy testing
Results are reviewed against the requirements established for the product and can help determine whether the formulation can continue through development or whether further work is required.
Microbiological testing may also sit alongside stability testing and other product-specific testing as part of the development process.
How Long Does Microbiological Testing Take?
Timing depends on the type of testing being completed.
Preservative efficacy testing takes place over a defined testing period because samples need to be assessed at scheduled intervals.
Other microbiological testing may have shorter testing periods, depending on the method being used.
Brands should allow for testing within the wider development timeline rather than assuming it can be completed immediately before production.
If further formulation work or repeat testing is required, additional time may also need to be allowed.
When Should Brands Discuss Microbiological Testing?
Testing requirements are worth discussing while the product is still in development.
Brands do not need to arrive with a microbiological testing plan already prepared. The formulation, quality and manufacturing teams can help identify what needs to be considered for the individual product.
Discussing testing early also gives the brand a more realistic understanding of what needs to happen between approving a lab sample and progressing towards commercial manufacturing.
How Microbiological Testing Fits Into the Bigger Picture
Microbiological testing is one part of product development. It should be considered alongside the formulation, stability testing, packaging and manufacturing requirements.
The information gathered through testing can help development and quality teams understand how the product is performing and whether anything needs to be reviewed before the next stage.
For brands, the goal is not to become a microbiology expert. It is to understand why testing is part of the development process and what information it provides.
Working With Delta
Delta works with cosmetic and personal care brands from formulation development through to commercial manufacturing.
Depending on the product, microbiological testing can be considered alongside formulation development, stability testing and other requirements as the product progresses.
Connecting these stages within the wider development process gives brands a clearer understanding of what needs to happen before a product moves into commercial production.
Need Support With Microbiological Testing?
Speak to Delta about your product, testing requirements and the next steps towards commercial manufacturing.