This is a new column created in collaboration with Lalita (@skinchemy on Instagram), a certified and professional cosmetic chemist. Each week, Lalita answers frequently asked skincare questions, based on results from existing scientific research!

Q: My vitamin c serum has oxidized. If I continue to use it, will it harm my skin?

A: The short answer is no.

Let’s talk about oxidized vitamin C serums. By this I mean, water-based vitamin C (L-ascorbic acid) serums. As we know, L-ascorbic acid is extremely unstable in the presence of water, oxygen and light. It degrades quickly and forms into a compound named dehydroascorbic acid (DHAA). DHAA is yellowish orange in color. When this happens to your serum, your serum is starting to degrade. ⁣⁣
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While you can certainly try to extend its shelf life by keeping it in a dark/cool place, if the formulation contains water, it’s almost inevitable. At some point, the vitamin c serum will start to degrade. Stabilizing ingredients, such as ferulic acid and vitamin E, can extend its shelf life. ⁣

Is oxidized vitamin C bad for my skin?

One thing I wanted to address, however, is that oxidized vitamin C serums are NOT bad for your skin. There are too many articles online stating that using oxidized vitamin C serums will speed up aging and can do a lot of harm.

However, as far as current research goes, we have not seen any studies that specifically show that oxidized vitamin C causes any skin damage to the skin. If anything, it just won’t do its job as well! This means that it would not be able to effectively fight free radicals when you’re out in the sun. But, that’s about it. It’s unlikely to cause any type of irritation or discomfort. ⁣⁣
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Always look for a product that contains more than one antioxidant, such as hyaluronic acid, ferulic acid, vitamin E, or green tea, as well as one that contains other effective “active” ingredients. This way, even if your product degrades due to the antioxidant, you can still continue to use it and benefit from the other ingredients. And, your money wouldn’t go to waste! ⁣⁣

Note from Picky: Check out this Instagram post for our vitamin c serum Picks!

Ready to find your own Holy Grail vitamin c serum? Download Picky on App Store now to discover products based on your desired ingredient combination!

Reproduced and recreated with permission from @skinchemy.