Stability testing is the process of evaluating a product to ensure that key attributes stay within acceptable specifications during the aging process. Physical test parameters include appearance, color, odor, viscosity, pH, and package compatibility as analyzed using microbiological and/or analytical testing.
It’s an effective way to determine the shelf-life, expiration date, and overall long-term performance of a range of products, including cosmetics, over-the-counter (OTC), personal care products, dietary supplements, and medical devices.
In this post, we’ll focus on cosmetic stability testing, which includes personal care products, and OTC stability tests.
The regulatory environment for stability testing for cosmetics, personal care products, and over-the-counter (OTC) products is nuanced, with distinct guidelines for each category:
Although not mandated under U.S. law, many cosmetic manufacturers perform stability testing on their products nonetheless for a few important reasons:
The FDA's approach to classifying a product as a cosmetic or a drug is based on claims, intended use, and sometimes formulation.
By law, cosmetics may only cleanse, beautify, promote attractiveness, or alter appearance.
In contrast, any product claiming to affect the structure or function of the body is considered a drug.
This regulatory distinction between cosmetics and drugs is crucial as it determines the subsequent regulatory requirements, including allowable ingredients, testing, and labeling.
Historically, cosmetics have had minimal FDA regulatory requirements, focusing mainly on marketing claims and intended use.
The Modernization of Cosmetics Reform Act (MoCRA) brings significant changes, aligning many cosmetic product requirements with those applicable to OTC-drugs, including mandatory Good Manufacturing Practices (GMPs), product registration, safety substantiation, and more.
An important aspect of product safety and quality assessments is testing for product degradation or stability. While MoCRA doesn’t explicitly require stability testing for cosmetics, many companies conduct these stability studies to determine appropriate cosmetic expiration dates when they might be required to ensure safety.
Stability protocols are designed to evaluate the stability of the product over time under different environmental conditions, such as temperature, humidity, and light exposure. There are essentially three types of tests that will be performed to evaluate the product during the stability study:
Microbial contamination can occur during manufacturing or after the product has been opened by the customer. They potentially introduce microbes each time they use the product.
This presents the opportunity for mold, yeast, or bacteria to contaminate the product and potentially cause an adverse reaction. Microbiological testing helps determine the effectiveness of the product's preservative system, known as preservative efficacy testing (PET).
At various time points throughout a stability testing protocol, microbiologists will perform quantitative analysis to determine the count levels of mold, yeast, or bacteria in the product. Quantitative analysis is superior to a simple screening test, which can only tell you if microbes are present, but not actual colony counts.
This type of testing evaluates how the cosmetic, personal care product, or OTC product reacts to stressors like temperature extremes, humidity, and light. It can evaluate the following characteristics:
The product is placed in a sealed chamber set to a specific temperature and humidity range. Many manufacturers test their products at elevated temperatures (e.g. 45°C/75% RH) for a specified time to provide a trend from which they can extrapolate its performance at room temperature over a longer period of time. This helps save time during R&D.
The product is pulled from the chamber at prescribed time points for analysis, then returned for continued testing until reaching the end of the time period (e.g. six months, 12 months, 5 years).
Humidity levels also play an important role. Imagine a customer purchasing your product and storing it in a bathroom its entire life exposed to extreme swings in humidity. You want to ensure your product can withstand that type of environment throughout its shelf life.
Labs use various conditions during stability testing to evaluate the product's performance, with the intent of challenging the product with the conditions most likely to be encountered once the product leaves the facility.
Certified Laboratories follows International Conference of Harmonization (ICH) guidelines and performs stability testing under the following conditions:
The packaging of a product plays a critical role in determining its shelf-life and overall stability. Chemical reactions between the product and its packaging can compromise performance. Additionally, packaging that isn't airtight may allow air or moisture to infiltrate, leading to product degradation.
To ensure product safety and quality, stability testing evaluates these potential interactions. Known as a "compatibility test," this process assesses how well the product and its packaging work together over time. It determines whether any adverse reactions occur, such as leaking, discoloration, or exposure to air, all of which can affect the product's quality or safety.
For the most accurate results, it's recommended to conduct stability testing using the product’s final packaging. This helps identify any potential issues and ensures the product remains effective and safe throughout its intended shelf life.
You can run a cosmetic or OTC stability test whenever your company needs product data, but best practices dictate performing a stability test when any of the following occur:
Stability testing is performed using calibrated storage chambers set to prescribed temperature and humidity settings.
Specific procedures for OTC or cosmetic shelf-life and stability testing vary depending on the product type, raw materials, and other factors. Be sure to follow the appropriate stability testing methods for OTC products or cosmetics, and to consult with a qualified professional to ensure that testing is conducted accurately and thoroughly.
That said, stability testing for OTC, cosmetic, and personal care products generally follows these steps:
International Conference on Harmonization (ICH) guidelines say that data from formal stability studies should be provided on at least three primary batches of the product. The batches should be manufactured to a minimum of pilot scale using the same manufacturing methods and procedures as production batches.
ICH guidelines recommend performing a stability study on the product packaged in a container that is the same or that simulates the containers that will be used during distribution and storage.
It is best practice to test the finished product as it will be marketed to gather data on how the packaging and product itself interact during storage.
Test the attributes of your product that are susceptible to change and that are likely to influence quality and safety. Testing should include the appropriate microbiological, chemical/physical, and packaging tests needed for your product.
At minimum, test appearance, odor, pH, and viscosity.
These readings take place at the initial time point and provide a baseline against which to compare results from future time points.
Next, store the product in a controlled, calibrated stability chamber set to the appropriate temperature and humidity. Exact settings will vary depending on the product and expected storage conditions, but ICH provides the following guidelines:
|
Study |
Storage condition |
Minimum time period covered |
|
Long-term* |
25°C ± 2°C/60% RH ± 5% RH Or 30°C ± 2°C/65% RH ± 5% RH |
12 months |
|
Intermediate** |
30°C ± 2°C/65% RH ± 5% RH |
6 months |
|
Accelerated |
40°C ± 2°C/75% RH ± 5% RH |
6 months |
* It is up to you to decide whether long-term stability studies are performed at 25°C ± 2°C/60% RH ± 5% RH or 30°C ± 2°C/65% RH ± 5% RH.
** If 30°C ± 2°C/65% RH ± 5% RH is the long-term condition, there is no intermediate condition.
The product is removed from the stability chamber at prescribed time points and evaluated. Results are compared to the baseline results gathered at time point zero.
How often the product is removed from storage and evaluated depends on the data you need, but there are industry best practices to consider:
ICH guidelines call for conducting an Intermediate study if significant changes occur to the product during an Accelerated stability study. In this case, a minimum of four time points for a 12-month study is recommended: time point zero, three months, six months, and 12 months.
Once the stability testing period has ended, the product is evaluated one final time.
Stability testing results are based on trends, which are time consuming to calculate. The final report will provide a good picture of your OTC, cosmetic, or personal care product’s stability during the test duration.
This information helps your company establish a recommended shelf-life and storage conditions that will promote product quality and safety. Stability test results can also help you substantiate the safety of your products for regulatory purposes.
Results of stability tests for cosmetics are based on trends, which take time and expertise to calculate.
Every OTC, cosmetic, and personal care product manufacturer should have a stability testing program to support product quality. The challenge arises when determining how to design tests for specific products.
Here are a few points to consider when designing a cosmetic stability test:
Designing an OTC or cosmetic stability test can be confusing if your organization is new to the process. You must test under the right parameters and follow industry regulations, which can be difficult to understand.
Our stability testing experts at Certified Laboratories have conducted thousands of stability tests on a range of cosmetic, personal care, OTC, supplements, and other products. We’re happy to walk through the process with you and ensure you’re getting the right data for your products. Get a quote for your stability testing protocol here.