No matter how effective or aesthetically appealing a cosmetic product may be, it must first and foremost be microbiologically safe. The moment a jar of cream or a bottle of shampoo is opened, it becomes exposed to air, fingers, applicators — and with them, to microbes. That’s why the preservative system must be tested and proven to work under real-world conditions.
At CE.way, we help brands ensure the microbiological safety of their products through a thorough, internationally recognized cosmetics challenge test — one of the most important steps in building a responsible and legally compliant cosmetic product.
What Is the Challenge Test?
The challenge test, also known as a Preservative Efficacy Test (PET), is designed to evaluate whether the preservatives in a cosmetic product are effective in protecting it from microbial contamination during its shelf life and use.
In the test, a finished product is intentionally inoculated with specific strains of bacteria, yeast, and mold. The product is then observed over a period of time to determine whether its preservative system can effectively eliminate or reduce microbial growth.
The most commonly used reference standard for this is the ISO 11930 protocol — which we apply in cooperation with trusted partner laboratories.
Why Is the Challenge Test Important?
While not legally mandatory for all products, the challenge test is highly recommended under EU Cosmetic Regulation (EC) No. 1223/2009, especially for products with high water content and products intended for repeated direct contact with skin.
It provides clear answers to critical questions:
- Is the preservative system strong enough to prevent microbial growth after opening?
- Will the product remain safe and stable throughout its shelf life?
- Can the formulation resist contamination from daily use?
For many retailers and regulatory bodies, results of a successful challenge test for cosmetics are considered essential to accept a product onto the market.
Who Needs It?
We strongly recommend challenge testing for any cosmetic product that contains water — such as creams, lotions, shampoos, conditioners, gels, toners, or micellar waters.
It is especially relevant for:
- Natural or organic cosmetics with milder preservatives
- Products intended for babies, sensitive skin, or the face
- Formulations stored in jars or pots where fingers touch the product
- Products manufactured in smaller batches or in non-sterile environments
Even products preserved with well-known systems (e.g., phenoxyethanol, parabens, sodium benzoate) must be tested in the context of the full formula, since preservatives behave differently depending on pH, viscosity, and packaging.
Our Process at CE.way
When we coordinate a challenge test, we take care of the entire process — so you don’t have to. Here’s how it works:
- Sample evaluation – We assess the formulation and packaging to determine which protocol is most appropriate.
- Lab coordination – We select a certified microbiology lab to conduct the test following ISO 11930.
- Test procedure – The lab inoculates the product with five standard microorganisms (3 bacteria, 1 yeast, 1 mold).
- Monitoring – Microbial counts are measured over a 28-day period.
- Final report – A full test report is provided, which you can include in your Product Information File (PIF) and use as part of your safety documentation.
You can learn more about our full range of cosmetic microbiological testing services, including stability, PET, and preservative system evaluation, directly on our platform.
More Than Just a Test — It’s Risk Management
Skipping the challenge test may seem like a shortcut in the early stages of product development — but it can turn into a serious risk down the road. Products that become contaminated after opening can cause irritation, infection, product recalls, or damage to brand reputation.
At CE.way, we help you build safety into your product, not just react to problems after they occur. Our support ensures that your preservative system works, your documentation is audit-ready, and your product is trusted by both regulators and consumers.
Because in today’s market, microbiological integrity is not optional — it’s expected.
