What is Skincare Oxidation?

Unpacking the science behind your products going bad.



2 MIN READ | FEBRUARY 19, 2021



Meg is the CEO and Co-founder of Atolla. She has a graduate degree in Engineering and Management from MIT, and previously worked in design roles at Patagonia, The MIT Design Lab, and Formlabs.

When it comes to skincare packaging, many brands opt to use glass bottles because they can be recycled after they’re cleaned if they’re undecorated (check out the Atolla sustainability guide here). Some glass bottles can actually be recycled multiple times without loss in quality or can be made into new glass products.

The downside to using glass is that it exposes the formula to sunlight, which can lead to concerns of formula oxidation. This means the ingredient has degraded and is no longer safe to use. Here’s how formulas can oxidize and how to tell if yours has.

What contributes to oxidation?

The size of your bottle (i.e. how many ounces) and how the product is made can definitely affect oxidation. A larger bottle runs a higher risk of not being finished before it starts degrading. Mass production also contributes to a higher risk of oxidation due to the products living longer on the shelf before actually being bought and used.

We make smaller (one-month) supplies of formula that are produced for immediate usage, so the bottle isn’t exposed to the sun for enough time to oxidize.  While your 15mL custom serum is intended to be used in 1 month, the actual stability is for 6 months or more (especially if you avoid putting it in direct sunlight). Learn more about our custom serum here.

How do I know if my skincare has oxidized?

Formulas with potent ingredients like Vitamin C can take around 4-5 months to oxidize. With a glass bottle, you would notice this oxidation with the formula changing to a brown color. With a darker bottle, you wouldn’t be able to see the oxidation visually but it might start to smell different or look darker when applied to your skin.

Keep in mind what color is considered “normal” for that formula’s ingredients. There may be specific ingredients combined with the Vitamin C that make it a red or orange color when you receive it, which would not mean it’s oxidized. As always, it’s best to ask the brands directly to understand their formulation process and product shelf life!

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