It's no secret vitamin C serum benefits skin in many ways. It’s an antioxidant, helps build collagen, and a skin brightener. For all this to happen, it needs to be in its purest form, L-Ascorbic Acid. But vitamin C's potency is also its largest downfall. It's so effective it starts to oxidize in the bottle!
Oxidize means to react with oxygen, once this happens it's turned into a completely different formulation (dehydro-L-ascorbic acid). This is exactly what's happened when your vitamin C serum start to turn brown.
I'm sensing your frustration, at this point you're thinking "Well how long does it last? How do I keep it from oxidizing?" or "Do I need to throw it out?".
First answer, your serum should last roughly three months after opening before starting to oxidize. Vivier's serums are stabilized, meaning they won't oxidize and turn brown on your skin... Some other brands do.
Secondly, since L-Ascorbic Acid reacts with oxygen, reduce the amount of oxygen exposure by resealing the bottle after every use. In addition, make sure your products are not in direct sunlight or heat. You don't need to refrigerate them (although some people do), just place it in a drawer if you're keeping it in the bathroom.
Lastly, it could be reduced by .01% or 10% or even 50%. You don't have to ditch it, but know that it may not be doing its best to help your skin.
Have you used a Vitamin C serum that turned yellow-brown in colour?
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