Cosmetic Stability Testing

Cosmetic stability testing evaluates whether a product's safety, quality, functionality and aesthetics are not adversely impacted throughout its intended shelf life and consumer use. 

What is stability testing in cosmetics?

As personal care products, or over-the-counter (OTC) products can age, testing must be conducted to monitor and assess key physical, chemical, and microbiological properties must remain within acceptable parameters to ensure the product performs as expected and is safe for consumers to use. 

Cosmetic stability testing helps innovators and manufacturers optmise formulations - particularly with regard to the choice of preservatives selected - in combination with preservative efficacy testing. A cosmetic stability test can also help determine shelf life, expiration dating, and long-term performance under real-world conditions.

How to stability test a cosmetic formula

With over 20 years of experience, our cosmetics stability testing team perform studies under controlled accelerated or real-time conditions. Our cosmetic stability testing labs focus on key specifications for the product including appearance, color, odor, viscosity, pH, microbiological quality, and compatibility with packaging. Analytical testing may also be included to evaluate active ingredients where applicable, such as vitamins, preservatives, or sunscreens.

Our experts provide:
Accelerated Stability Testing Cosmetic Products: Ideal when targeting a shelf-life of more than 30 months to avoid displaying an expiration date on packaging.
Cosmetic Stability Test: Conducted in the most inert packaging available, independent of the final packaging—to assess how the product behaves under various conditions, including Accelerated Light Aging.
Compatibility Study: Performed using the final packaging to evaluate potential interactions between the formula and its container across different environmental conditions.
PAO (Period After Opening) Study: Determines how long a product remains stable, effective, and safe once opened.
We also provide physico-mechanical testing of packaging components and climatic cycling tests to simulate real-world transport and storage environments.
Analytical Testing: With over 20 years of experience we perform all aspects of cosmetics analysis including determination levels of active ingredients (preservatives, vitamins, preservatives and more).
Packaging Migration testing: We perform packaging migration testing and screening for non-intentionally added substance (NIAS) for plastics or recycled plastics (CosPaTox, etc.)

Chemical and physical property stability testing - cosmetics

During stability testing of cosmetics, typical chemical and physical testing parameters we evaluate, help assess how a product responds to environmental factors such as temperature, humidity, time in storage. During accelerated stability testing for cosmetics (50°C), we use elevated temperatures to identify trends and predict long-term behavior at normal storage conditions, helping shorten development timelines. We can also perform climatic cycling tests to replicate real-world transport and storage conditions. Common parameters include:

• Appearance and color
• Odor
• pH
• Viscosity
• Specific gravity
• Package compatibility

Packaging compatibility and packaging performance testing

Interactions between the cosmetic formulation and packaging materials can lead to degradation, discoloration, leaking, or loss of product efficacy and negatively impact the product's microbiological integrity. Compatibility testing evaluates whether the primary packaging adequately protects the bulk product throughout its shelf life. For accurate results, stability studies should be conducted using the product’s final marketed packaging whenever possible. We look at the bulk product appearance, colour, odor, density, alcoholic volume content and mass loss. We also evaulate packaging appearance and product functionality.

For packaging performance, we evaluate vacuum leak testing, locking system resistance, pump priming, and dose delivery. We can also perform a range of packging functionality tests that include opening force of caps, thread integrity, actuation force, rotating mechanisms (e.g. for lipsticks), adhesive strengths and drop tests. 

Regulatory requirements for OTC stability or cosmetics stability

Demonstrating the stability of a cosmetic or an OTC product can vary across regions and product type. In Europe, Regulation (EC) No 1223/2009 requires that a cosmetic products undergoes a safety assessment prior to being placed on the market which includes stability testing of the cosmetics product under foreseeable storage conditions. 

In the United States of America there are no regulations that require cosmetics to have specific shelf lives or have expiration dates on their labels. However, manufacturers are responsible for making sure their products are safe. The FDA considers determining a product’s shelf life to be part of the manufacturer’s responsibility. It is important to note that not all personal care products are regulated as cosmetics in the USA. Some, such as sunscreen products and acne treatments, are drugs under US law and therefore are subject to different testing requirements.

Cosmetic stability storage conditions