One of the more frequent questions received here at Chemists Corner is about the expiration date of products. Formulators, and beauty product consumers alike, want to know how long a formula will last. Unfortunately, there is no simple answer but here are some guidelines to determining the expiration date of a cosmetic formula.
What is expiring?
Before we can talk about an expiration date, it makes sense to first define what is meant by “expiring.” When it comes to cosmetics, there are various things that indicate a product has expired.
Continues to work – A good indication of whether a cosmetic has expired is if it continues to work. If a product stops providing the benefit for which you use it, then it is expired. If a shampoo doesn’t clean your hair or a moisturizer doesn’t sooth your skin, the product has expired. However, the way that most cosmetic products are formulated, it’s pretty rare that a product stops working completely. Even a 10-years-old body was will still clean skin to some extent.
Has acceptable aesthetics – Perhaps a more important indication of whether a product has expired is whether it continues to be aesthetically pleasing to use. Over time, there can be chemical reactions going on in your product which can result in color changes, odor changes, pH drift, viscosity changes, texture changes and more. While these products might technically continue to work, they aren’t as pleasing to use as they were when you first bought them, so the manufacturer would consider them “expired.”
Meets specifications – Since aesthetics is a subjective characteristic, it would be difficult to define an expiration date based on that. For this reason characteristics of products are quantified through testing and a specification (numerical range) is set. That way you can say a product has expired if it no longer meets the specifications originally set out. So, if the viscosity of a body wash had a specification range of 5000 cps – 8000 cps, the product can be considered expired if the viscosity range ever goes higher or lower than the specification.
How do determine cosmetic expiration dates
By defining an expiration point as the time when the product no longer meets specifications, you can then run a test to determine an approximate expiration date. The industry standard way of doing this is called stability testing.
Stability testing – Stability testing involves an experiment in which you take samples of your product and put them at different environmental conditions for a set period of time. The conditions vary in temperature and light levels and are meant to simulate what happens to the product during its life cycle from shipping, to store shelves, to consumer’s bathrooms.
At select intervals you evaluate your samples for various physical, chemical and performance characteristics to see how they have changed. If the changes are minimal according to your company standards, then the product is still good. When characteristics of the product go outside of the specified ranges, then your product can be said to have “expired.” See this post for more information on cosmetic stability testing.
Types of products – The exact type of characteristics you measure in a stability test will vary depending on the type of product but for most cosmetics the following are usually tested.
- pH (aqueous based products)
- Microbial challenge testing
Manufacturers and consumers likely have different expectations for how long a product should last. For most products, the industry standard is that it should be stable for at least one year. This means you shouldn’t expect to see any changes for characteristics outside the specification range after one year of testing. Of course, if the product isn’t selling fast enough the manufacturer would like this date extended but they also strive to have all inventory sold before one year.
Consumer expectations – Consumers are a bit different in that they want to have products that will last for as long as they have it. They don’t really want to buy a product that will “go bad” in a short amount of time. Actually, I don’t think they want products that will go bad for however long they have the product. This can be a really long time. In fact, I’ve got a men’s hair styling product that is at least 10 years old. I still use it on occasion because it smells fine and still works. This is why I make a terrible target consumer for hair products.
Government expiration expectations – It’s interesting to note that in the US there is no specific requirement to put an expiration date on a cosmetic product. It is a law however, that the manufacturer has to run tests to determine the shelf life to demonstrate the product is safe to use. In the EU there are more stringent requirements for product expiration dates. If a product has an expected shelf life of longer that 30 months you must do testing to demonstrate how long the product will last after opening. If the product has a shorter than 30 month shelf life, you must put a “best before” date on the package.
Expiration of cosmetic products
As a formulator, it’s helpful to know that different products can have different expiration expectations. Or at least there is a consumer perception of cosmetic expiration. Expiration dating isn’t an exact science but here is a guideline you can follow for how long various products are expected to last.
- 3 months – eye makeup
- 6 months – Anti-aging creams, vitamin C products
- 9 – 12 months – Cream color cosmetics, lip gloss
- 12 months – powder color cosmetics
- 24 months – shampoos, conditioners, body wash, moisturizers, most everything
- longer – Anything that still smells & looks good (which probably won’t be much)