How do you know when your serum expires?

Check the bottle and outer packaging for an expiration date or an open jar symbol. The jar symbol, called Period After Opening, shows a number followed by M: that number tells you how many months the product should last after opening. For example, 9M means nine months after you first open it, not nine months after you buy it.2

Cosmetic serums do not have to carry an expiration date in the United States, so a blank label is not a declaration of immortality. If there is no date or opening symbol, ask the manufacturer how long to keep that specific formula, including how long an unopened bottle lasts. Sunscreen and acne treatments follow different rules because they are regulated as drugs and require expiration dates.1

Write the opening date on the container so you can track its age. An open jar symbol tells you months after opening, but it does not keep a diary for you.23

What changes mean you should throw it away?

Throw away serum if its color or smell changes. Separation, drying out, or a changed texture are also signs that a cosmetic formula has deteriorated. Compare the serum with how it looked and smelled when new, rather than treating any particular color as automatically bad. Heat, sunlight and air can change a product before its expected lifespan ends.13

How should you store serum?

  • Follow the label's storage instructions and directions.
  • Keep the container clean and tightly closed between uses.
  • Protect serum from temperature extremes, especially a hot car.
  • Avoid damp storage conditions: bathroom moisture can make it easier for bacteria and fungi to grow.
  • Wash your hands before using serum, and keep applicators clean. Dipping fingers into a product introduces microorganisms.
13

What if an old serum causes a reaction?

Stop using the serum if you develop a rash, redness, burning or another unexpected reaction, and contact your healthcare provider for advice on managing it. You can also report the reaction, or a product problem such as a bad smell or foreign material, to the FDA.3

Where this answer comes from

  1. 1Shelf Life and Expiration Dating of Cosmeticsfda.gov
  2. 2When to toss your makeup and sunscreenaad.org
  3. 3Using Cosmetics Safelyfda.gov