Reviewed and Approved by Anjali Krishnan, PhD, Technical Manager-Microbiology Certified Laboratories; Lisa El-Shall, Sr. Director of Drug and Device Consulting, EAS Consulting Group; Jeb Hunter, Senior Regulatory Consultant, EAS Consulting Group
1-Minute Summary
- PET verifies the effectiveness of preservatives at preventing microbial growth in cosmetic and OTC products.
- PET, AET, and Cosmetic Challenge Testing are interchangeable terms for the same testing.
- Factors like ingredient interactions, packaging, storage conditions, and consumer usage affect potential microbial growth.
- PET typically requires 5-6 weeks, including incubation and microbial analysis phases.
What is Preservative Efficacy Testing (PET)?
Preservative Efficacy Testing (PET) evaluates the effectiveness of a cosmetic or over-the-counter (OTC) pharmaceutical product's preservative system, which is designed to inhibit the growth of microorganisms that could be introduced during manufacturing or by users during regular use.
By simulating these conditions, preservative efficacy testing helps determine if products are capable of remaining free from harmful microbes, safeguarding consumer health and maintaining product integrity.
This testing is a critical safety and quality assurance measure for manufacturers in the health and beauty industries.
Clarification of Terms: PET, AET, and Cosmetic Challenge Testing
Several terms are used to describe the process of testing the effectiveness of preservatives in cosmetic and OTC products. Often used interchangeably, they refer to the same essential testing protocol:
- Preservative Efficacy Testing (PET): This term is commonly used across various industries to denote the testing of a product's ability to inhibit microbial growth.
- Antimicrobial Effectiveness Testing (AET): Equivalent to PET, AET is another commonly used term that emphasizes the antimicrobial aspect of the testing.
- Cosmetic Challenge Testing: Specifically used in the context of cosmetics, this term refers to the same process as PET and AET, highlighting its application in cosmetic product safety.
These terms all describe a standardized protocol for assessing whether a product's preservative system can effectively control microbial growth under simulated-use conditions.
Is PET a Regulatory Requirement for Cosmetics?
Regulations differ depending on the market where you intend to sell the cosmetic product. In the United States, the FDA regulates cosmetic products primarily via the Federal Food, Drug, and Cosmetic Act (FD&C Act).
The FDA says on its website that, “Companies and individuals who manufacture or market cosmetics have a legal responsibility to ensure the safety of their products.”
Furthermore, 21 U.S.C. § 364d says, “A responsible person for a cosmetic product shall ensure, and maintain records supporting, that there is adequate substantiation of safety of such cosmetic product.”
The regulation goes on to define safety substantiation as “…tests or studies, research, analyses, or other evidence or information that is considered, among experts qualified by scientific training and experience to evaluate the safety of cosmetic products and their ingredients, sufficient to support a reasonable certainty that a cosmetic product is safe.”
While the U.S. regulations don’t prescribe Preservative Efficacy Testing by name, it helps fulfill your regulatory requirement to substantiate product safety prior to marketing your cosmetic products in the U.S.
Is PET a Regulatory Requirement for OTC Products?
In the U.S., manufacturers must follow current Good Manufacturing Practices (cGMPs) outlined in 21 CFR 211. Like cosmetic products, PET isn’t specifically required by name per the regulations. However, manufacturers are responsible for ensuring the safety of their products, and many perform Preservative Efficacy Testing to verify the integrity of the preservative system during storage, particularly for aqueous-based formulations .
PET can also be part of a robust stability testing program, which is a requirement of 21 CFR 211.166.
What Factors Can Affect Preservative Efficacy?
The effectiveness of preservatives in cosmetics and OTC products can be influenced by several key factors:
Ingredients and Formulation
- Active and Excipient Ingredients: The specific preservatives chosen and their concentrations are crucial. Some ingredients may have synergistic effects that enhance preservative efficacy, while others might interact negatively, reducing effectiveness.
- Product pH: The pH of the product can affect the solubility and ionization state of preservatives, impacting their ability to inhibit microbial growth.
- Compatibility: Components of the formulation should be compatible with the preservative system. Incompatible ingredients can deactivate preservatives, making the product susceptible to microbial contamination. In addition, the nature of the compound, such as whether it is anhydrous or not, plays a role since that will determine the recommended test.
Packaging
- Material: Packaging materials should be chosen to ensure they do not react with, absorb, or leach out the preservatives, which could decrease their effectiveness.
- Design: Packaging design should minimize exposure to air and contaminants. Pumps, airless dispensers, or single-use formats can enhance preservative efficacy by limiting product exposure to the environment and reducing contamination during use.
Storage Conditions
- Temperature: High temperatures can enhance the growth of microorganisms and degrade preservatives, reducing their effectiveness. Conversely, extremely low temperatures might inhibit the activity of some preservatives.
- Humidity: Increased humidity can provide a favorable environment for microbial growth, especially in products exposed to air. Products stored in high-humidity conditions may require more robust preservation.
Consumer Use
- Usage Patterns: Frequent opening of containers and the method of application (e.g., dipping fingers into products) can introduce microorganisms. Products designed for frequent consumer handling may need stronger or more resilient preservative systems.
- Storage by Consumers: How consumers store the product (e.g., in a damp bathroom vs. a dry cupboard) can also affect the longevity and effectiveness of the preservative system.
Understanding these factors is critical for ensuring the preservative system helps the product remain safe and stable throughout its intended shelf-life and usage.
How is Preservative Efficacy Testing Performed?
Preservative Efficacy Testing follows a series of standardized steps designed to assess the effectiveness of a preservative system. These procedures ensure that the product remains safe and stable under the intended usage conditions by effectively controlling microbial growth. Here's an overview of the typical PET testing process:
Inoculation
Products are inoculated with a set of microorganisms to simulate contamination that could occur during use, typically including bacteria, yeasts, and molds. Common organisms used in PET include…
- Pseudomonas aeruginosa
- Staphylococcus aureus
- Escherichia coli
- Candida albicans
- Aspergillus brasiliensis
Incubation
The inoculated product is stored under controlled conditions, usually at room temperature (20-25°C), for 28 days.
Sampling and Analysis
Microbial counts are typically measured at specific intervals throughout the incubation period, commonly on days 2, 7, 14, 21, and 28.
Microbiological techniques such as plate counts are used to assess the number of viable microorganisms remaining at each interval. The effectiveness of the preservative is determined based on its ability to reduce the microbial population over time.
Criteria for Success
Successful preservative efficacy is generally indicated by a logarithmic reduction in the number of viable microorganisms. For instance, guidelines might require a 3-log reduction (99.9% reduction) of bacteria and a 1-log reduction (90% reduction) of fungi within specific time frames.
The specific criteria for success can vary based on regulatory guidelines, such as those from the USP, PCPC M-3/M-6, ISO, or European Pharmacopoeia.
How Long Does PET Take?
Consider the time needed to process your sample, 28-day incubation time, time to conduct microbiological assays, and report generation. For those reasons, plan on 35-38 days to receive results for PET testing.
Also, it’s advisable to set aside both bulk product and finished packaging for PET testing to simulate real-world conditions and assess the preservative system’s effectiveness at preventing microbial growth.
Where Can I Find PET Testing?
Certified Laboratories provides Preservative Efficacy Testing (PET), Antimicrobial Effectiveness Testing (AET), and Cosmetic Challenge Testing – in addition to routine microbiology testing – for a variety of cosmetic and OTC products. Our labs are ISO 17025-accredited and FDA-registered for testing OTC products.
Contact us for a quote for your testing.
If you need assistance deciphering U.S. cosmetic and OTC regulations, EAS Consulting Group, our regulatory arm, can help.
