Preservative Efficacy Test (Challenge Test) : Ensuring the Microbiological Safety of Your Cosmetic Products
Cosmetic products, especially those with water-based formulations, are prone to microbial contamination during storage or consumer use. To ensure product stability and consumer safety throughout the entire shelf life, Preservative Efficacy Testing (PET)—also known as the Challenge Test—is a critical component of quality control.
ME-COS LAB provides internationally compliant Challenge Test services, certified by TAF, to evaluate the effectiveness of your product’s preservative system against harmful microorganisms. Our testing ensures both regulatory compliance and product safety.
Purpose of the Challenge Test
The Challenge Test simulates real-life contamination scenarios by intentionally introducing specific microorganisms into the product, to assess how effectively the preservative system can inhibit or eliminate them over time.
This test is essential for:
Water-based formulations (lotions, creams, gels, toners, etc.)
New product development or formula modifications
Safety dossiers for regulatory registration and product claims
Standard Test Microorganisms
Following international standards such as ISO 11930, the Challenge Test targets five key microorganisms, representing a range of contamination risks:
☐ Aspergillus brasiliensis – A common mold, indicates long-term preservation risk
☐ Candida albicans – A yeast species, relevant for lip, mucosal, and intimate area products
☐ Escherichia coli – Represents fecal and environmental contamination
☐ Staphylococcus aureus subsp. aureus – A common skin pathogen
☐ Pseudomonas aeruginosa – A water-loving bacterium resistant to many preservatives
These species are commonly found in regulatory guidance for testing the robustness of preservative systems.
Testing Procedure and Time Points
During the Challenge Test, your product is intentionally inoculated with a controlled mixture of the five microorganisms. We then measure microbial reduction and control at key time points:
Day 7
Day 14
Day 28
Based on ISO 11930 or region-specific regulations, the microbial count is expected to show significant reduction (log reduction) or continued inhibition to meet the criteria for passing the test.
Why Choose ME-COS LAB?
TAF-accredited laboratory: Reports recognized for regulatory submission
Use of standardized strains and validated protocols
Compliance with ISO 11930 and tailored challenge test solutions
Fast turnaround times to support time-sensitive product launches
Can be integrated with microbial limit tests and stability testing for efficiency