Has Your Skincare Gone Rancid? How To Spot Oxidation In Skincare Products?

When you leave an apple out on the counter, it eventually turns brown. Don’t let that happen to your skincare products!
BY Sarah Lim
| Last updated Apr, 2023
oxidized vitamin c

Unless your skincare routine consists of only honey (which literally lasts forever), your precious serums and moisturizers are bound to go wrong—depending on the specific product and formula. The rotting happens within a few months or up to a year. That’s right: skincare products can and do expire, and some even oxidize. It can essentially cause your product to go wrong, such as in oxidized vitamin C.

These rancid products are most often ineffective. But even worse, they may affect the health of your skin if you continue to use them after they’ve gone bad. But what exactly is oxidation in skincare products, and how can you tell if a product is past its “prime”? We’ve got all the details on oxidation in your skincare products!

What Is Oxidation In Skincare Products?

If you’ve ever seen an avocado or apple turning brown after you’ve sliced it, you’ve seen oxidation. 

Oxidation is a natural process, essentially a chemical reaction in which molecules lose their electrons. In short, oxidation changes the chemical structure of the ingredients in your product.

The result? The color of the product may change—as well as the consistency and integrity of the ingredients. The product may not be as potent, which means it could be less effective. 

Like oxidation, it turns out that oxidation can impact your skincare products’ integrity. So oxidation can make fruits and veggies lose some of their nutrients as they become riper and eventually start rotting.

Oxidation even happens to us as we age and causes natural changes in the skin over time. However, oxidation that causes skin aging can become accelerated, namely by conditions such as inflammation and skin cancer.

We know the signs that we’re beginning to age, but spotting oxidation in skincare products can be a bit more tricky.

How To Tell If You Have Oxidized Vitamin C

how to tell if you have oxidized vitamin c

One of the products most at risk for oxidation is vitamin C. It is designed to protect skin from free radicals. Thus vitamin C can accelerate oxidation and damage DNA to cause inflammation. However, when vitamin C oxidizes, it can be ineffective.

Vitamin C can be beneficial for many skin conditions, from inflammation to wound healing to brightening your complexion. However, the most popular form of vitamin C, ascorbic acid, is relatively unstable as a skincare ingredient and is prone to oxidation.

Oil-based forms of vitamin C are less prone to oxidation. But these tend to be less effective than our bestie ascorbic acid. For example, ascorbic palmitate, an oil-based form of vitamin C, is also used as an antioxidant. It prevents foods from oxidation and is less likely to oxidize in skincare products.

Will applying oxidized vitamin C to your skin hurt you? The answer is generally “no”. Oxidized vitamin C won’t be very effective and, in rare cases, can cause the skin to turn yellow after applying, but it doesn’t generally hurt skin—it just doesn’t help it much either!

Oxidation Can Occur In Other Skincare Ingredients

There are other skincare ingredients besides vitamin C that can oxidize.

Retinol is another product that can oxidize over time. As retinol is continually exposed to air—for example, if your retinol product comes in a jar—it can turn yellow. However, yellowing doesn’t necessarily mean your retinol is oxidized.

If your retinol product oxidizes, it may not show any signs, including any change in color or smell. However, retinol can still be bad. Most importantly, what you can do is toss your retinol product after it becomes expired.

Much like vitamin C, you can protect retinol from oxidation by using oils in the formula. Light and oxygen can both impact the integrity of a retinol product over time.

Although oils can themselves oxidize and go rancid, certain oils are more resistant to oxidation than others. For example, jojoba oil is generally more resistant to the oxidation process and you can use it in combination with many ingredients in skincare products.

Typically, any skincare formulas that are more natural—meaning they contain fewer preservatives—tend to go bad faster than products full of chemical preservatives. 

Packaging And Storage Affects Oxidation

Packaging and Storage Affects Oxidation

Packaging and storage of your skincare products absolutely affect the oxidation process. For example, products stored in jars typically oxidize much faster than products stored in bottles with airless pumps. It is because every time you open the jar, the product becomes exposed to air.

The color of the container can also influence oxidation. That is why you’ll generally see vitamin C and retinol products stored in dark bottles, which can help protect them from light.

Encapsulation of the active ingredient can also prevent oxidation, for example, encapsulated retinol.

The good news is that most of these products that are more at risk of going rancid, such as vitamin C, are already stored in packaging that’s designed to slow the oxidation process as much as possible.

Below is the list of additional steps that you can do to help prevent oxidized vitamin C and retinol:

  • Always toss your skincare products by the expiration date (or if a product says “6 months” on the label, you should toss six months after opening the product).
  • Store your retinol and vitamin C—and any other ingredients that are prone to oxidation—in a cool, dark place.
  • In case your skincare products come in a jar, use a sterilized spatula or spoon to prevent bacterial contamination of the product, and always close it tightly after using.
  • When looking for a vitamin C product, a pump is generally best.
  • When looking for a retinol product, consider products that combine retinol with oils to prevent rapid oxidation of the product.

If you suspect your skincare product is terrible—this is usually a change in consistency, color, or smell—use your best judgment and toss it!

Are You Tossing Your Products on Time?

When was the last time for you to clean out your posse of skincare products or to check the label for their shelf-life? Consider this “your sign” to go through your products, and while you’re here, grab your free checklist on the skincare ingredients to avoid when you stock up on new products!


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1 Comment

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