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Ask a Dermatologist and a Chemist: Does a Serum Have a General “Shelf Life”? What Active Ingredients Tend to "Go Bad" or Lose Their Efficacy the Fastest?

Ask a Dermatologist and a Chemist: Does a Serum Have a General “Shelf Life”? What Active Ingredients Tend to "Go Bad" or Lose Their Efficacy the Fastest?

Dr. Courtney Rubin, our Chief Medical Officer, and Lizzy Trelstad, our Head of Chemistry, weigh in on your most pressing skincare questions.

Dr. Courtney Rubin’s take:

Most serums or treatments have a true shelf life of about 6-12 months. The best way to evaluate the shelf life of a particular serum is to check the box for an expiration date or to contact the brand and ask them for specifics, as each formulation is slightly different. A well-formulated serum should remain effective throughout its entire shelf life without the user having to worry about specific ingredients spoiling or losing efficacy. That being said, certain active ingredients are known to be unstable when exposed to light and air. Vitamin C, for example, can be volatile, so I recommend looking for formulas where vitamin C is combined with stabilizing companion ingredients, like vitamin E and ferulic acid.

I also recommend seeking out active formulas, especially vitamin C and retinol treatments, that have air- and light-tight, opaque packaging. Think of packaging as part of your active delivery system. If an ingredient has to be exposed to air, light and germs when using a product, it’s more likely to degrade over time.

At Fig.1, packaging is just as important as the formula itself. Our treatments are packed in airless, opaque and refillable cartridges, ensuring the actives inside are always protected. Plus, ours is a more sustainable packaging system!

Lizzy’s take:

Don't worry so much about using up serums before they go bad. I know it's so satisfying to get to the end of something, but I’d encourage you to use a particular serum only when your skin needs it. You may find that you grow out of needing a serum before the dropper goes dry. Don't let the bottle try to influence how, and how often, you use a product; let your skin and mood do so instead!

I will also add that the "freshness" of a product is generally a myth: all skincare products are generally safe to use for 6-12 months, depending on the specific ingredients. If a product is formulated, packaged and stored correctly, all ingredients, including actives, will be able to do their jobs just as well on day 1 as on day 124.

Usually, products "go bad" if (1) they're stored in clear glass, or require you to put your fingers in the formula; (2) the jar is stored on a windowsill, or in any other humid and sunny spot; (3) the formula is made without a robust preservative system. It's rarely an active's instability that makes a product spoil; it's usually packaging, storage or preservation errors. It’s a poor combination when vitamin A, C and E oils, or vitamin C, E, and ferulic acid serums, are packaged in clear glass jars with open-air lids.