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What It Actually Means When Your Serum Has Turned Brown

The bountiful benefits not may not last as long as you think.

Plus, whether it's okay or not to actually use it...

Vitamin C is a veritable wonder ingredient for skin and its benefits are plenty; but to deliver all its goodness effectively, the vitamin needs to be in the potent, and unstable form, known as L-ascorbic acid. But how long is it's shelf life? 


Vitamin C, famous for being found in citrus fruits, is an antioxidant, (see you later environmental ageing), it’s a collagen builder (hello voluminous skin) and it’s a skin tone brightener (welcome youthful glow). 

Vitamin C is by way of association, often as is thought of as orange, but in reality, vitamin C dissolved into water is not orange at all. It’s clear. As clear as water. 

Which in turn means, your Vitamin C serum should also be clear.


If you're a Vitamin C veteran, you'll know that the potency of your serum has more weight than just the L-ascorbic acid percentage, but also about its bioavailability, i.e. how well the overall formula delivers the goodness to your skin and the shelf life of the product. 

With a skincare ingredient like Vitamin C, it may well be stable for three years in a closed bottle, but when it’s opened daily for use, the shelf-life now becomes in-use life and the three-year shelf life expectation goes out the window.


Vitamin C is such an effective anti-oxidant, its chemistry isn't limited to skin-contact. As soon as the product is opened, it's active in the bottle and the compounds begin to change.

This is exactly what happens when Vitamin C serums turn brown. Vitamin C has oxidised (reacted with oxygen) and turned into dehydro-L-ascorbic acid and eventually diketogulonic acid.

The yellow-brown colour change is a visual sign of chemistry change. It shows that your Vitamin C serum no longer just contains L-ascorbic acid, the skin active form of the vitamin. 

So, In Short...

The more Vitamin C there is in your serum, the clearer it will be. The more ‘oxidation products’ there are in your Vitamin C serum the more brown it will be, meaning less of serum's benefits are available for your skin – oxygen from the air has gotten to them first.

While the oxidisation of Vitamin C can't be stopped, it can be slowed down through limiting its exposure to heat, light and air.

  • Heat - It's not essential to refrigerate your Vitamin C serum but it help to prolong its in-use life.
  • Light - Try minimise through storing in a draw or in shade. 
  • Air - After use, replace the lid quickly and tightly.

Main image by @boobie_billie on Instagram

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