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
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.
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:
These terms all describe a standardized protocol for assessing whether a product's preservative system can effectively control microbial growth under simulated-use conditions.
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.
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.
The effectiveness of preservatives in cosmetics and OTC products can be influenced by several key factors:
Understanding these factors is critical for ensuring the preservative system helps the product remain safe and stable throughout its intended shelf-life and usage.
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:
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…
The inoculated product is stored under controlled conditions, usually at room temperature (20-25°C), for 28 days.
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.
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.
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.
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.