unstable cosmetic

Article by: Perry Romanowski

In Colin’s post on nail polish, he reminded me of a common question I’m asked about beauty products and cosmetics is “how long do they last?”. Most people are hesitant to throw out any product they haven’t finished so they typically have a bathroom cabinet filled with old cosmetics. Even I have some skin lotions that are at least 5 years old.

As a cosmetic formulator, you should have a good idea of how long these things last. Here is an estimation of types of products and how long they last.

Two years or more

When you are formulating, your goal should be to create a product that will pass stability testing for at least a year. So, products that last longer than this are going to be robust formulas that are not exposed to temperature extremes or intense lighting. The most stable formulations will be the ones that have ingredients that are all compatible, don’t evaporate, and are stored in light-proof bottles. They will most likely be anhydrous, or solutions (rather than emulsions) and have air-tight containers which don’t allow for significant weight loss. Some of the best candidates for products that will last this long include.
Clear Shampoos
Clear Body Washes
Fragrances (in dark bottles)
Nail polish
Aerosols (hair spray, shaving cream, AP/Deo)
After-shave
Hairdressing
Bath oils
Powder color cosmetics
Soaps
Lipstick / lip balm

One year to two years

When you start creating emulsions you reduce the stability of the products and they don’t last as long. But every well-formulated cosmetic should last at least a year. Here is a list of formulations that fall into this category.
Pearlized shampoos / body washes
Dandruf shampoo
Facial scrubs
Hair conditioners
Skin lotions / moisturizers
Liquid foundation / eyeliner / blush
Clear bottle products
Hair gels
Styling products
Sunscreens

Less than a year

There are a number of cosmetic products that are reactive and have a limited shelf life or they are not formulated to last. Here are some of the shortest lasting cosmetic formulas.
Products without preservatives
“Natural” cosmetics
Hair colorants
Depilatories
Products with high fragrance levels
Relaxers
Sunless tanners
Opened products that aren’t sealed properly

Warning signs: Products that are no longer good to use will typically start to smell funny, change color, taste different or feel different. But unless they are contaminated with microbes they should still be functional. This post about 5 ways beauty products go bad elaborates more.

2 comments

  1. Kai

    Hi Perry! I am am making massage creams with a very simple formula. Water + Oil + Emulsifying Wax. And I can’t seem to find the right preservative to use. I have tried using 1ml of phenoxyethanol for a 1kg expected final product. Please help.

    1. Perry Romanowski

      I’d suggest you post your question in our forum. http://chemistscorner.com/cosmeticsciencetalk Also, give the % and exact ingredients you are using. 1 ml of Phenoxyethanol in 1kg of product isn’t nearly enough. You would need anywhere from 5 – 10 ml or another preservative.

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