I stumble upon some of the most interesting things while going through the Internet. Back in 2004 the CTFA (now the PCPC) and its EU sister organization COLIPA issued some Guidelines on Stability Testing. We have previously written about cosmetic stability testing which was strictly based on experience. Let’s see how our stability advice stacks up.
Stability testing Objective
According to the report, the objective of stability testing is to ensure that products meet chemical, microbiological and performance standards.
Yep, that’s pretty much why you do stability testing. The other important part is that it provides a paper trail for you to help prove that you are only selling safe products.
Stability testing design
A cosmetic stability test should be designed to assure
- Stability and physical integrity of cosmetic products under appropriate conditions of storage, transport and use,
- Chemical stability,
- Microbiological stability,
- The compatibility between the contents and the container
Indeed, this makes sense. This means you have to test the products under different conditions, in the right packaging, and do microbiological testing. The system we have described in our stability testing post meets these requirements.
Interestingly, they hedge their bets by saying that “Because of the wide variety of cosmetic products and their inherent complexity, ‘standard’ stability tests cannot be prescribed.” That is a good point but if you are creating a standard product, there are standard methods you can follow.
Predicting shelf life
One of the most common questions we get asked is “how much time at accelerated temperature will predict 1 or 2 years of stability testing”. The rule of thumb that I have always followed is that a sample stored at 45C for 8 weeks will predict how the sample will behave when stored at room temperature for 1 year.
The COLIPA guidelines do not give any such recommendations. This is typical of political organizations. They never want to say anything too specific. In truth, the 45C for 8 weeks is just a guideline and it may not work for every formula.
What to test in stability tests
The guidelines give a good description of the things you should test including
- Color, odor and appearance,
- Changes in the container,
- Weight changes
- Microbial tests demonstrating the ability of the products to prohibit microbial growth during normal use and other specific tests if necessary,
- Analytical data in relation to other parameters for specific product types
Finally, the COLIPA guidelines suggest that stability samples should be put under additional stress such as Freeze/thaw testing and light exposure. This is a good practice. I’ve seen numerous samples change color and fragrance character when exposed to UV light. This will happen to any product that is sold in stores under fluorescent lighting.
The guideline ends with some tips on creating your own cosmetic stability test protocol. You are free to create one based on these testing guidelines or you can just follow the system that we’ve already written about.
Just remember, stability testing is crucial to ensure your product is safe, of high quality, and remains functional. You can not launch a product without it.