The Reason Vitamin C Serum Can Darken Your Skin (And How to Stop It from Happening)

Serum staining your face and fingers? Here's what to know.
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Vitamin C serum darkens skin

Ever used a vitamin C serum and noticed your skin looking darker, orange or more tanned? 

You're not alone—this is a known side effect of the popular brightening and anti-aging ingredient!

But could the colour change actually be harming your skin? And is there a way to stop it from happening in the first place? Here's a recent question from my inbox:

I bought the Timeless 20% C + E + Ferulic Acid Serum, but I have doubts about using it in hot weather. I heard that vitamin C should only be used in winter because it can cause damage to the skin, like stains, when it is exposed to the sun. I want to go to the beach and have some sun, but I don't know if it is safe, even with sunscreen. Should I open the serum or save it for the winter?— Patricia

So, there are definitely some skincare ingredients to consider avoiding when you are getting a lot of sun exposure, at least during the daytime (if not altogether). Alpha-hydroxy acids such as glycolic acid and lactic acid are known to increase sun sensitivity. The same goes for retinoids, which are linked to phototoxicity, lipid peroxidation and DNA damage in UV light.

But vitamin C? It's an ingredient you can safely use year-round! In this article, I'll explain:

  • Why vitamin C is in fact beneficial when you're getting UV exposure
  • What causes vitamin C serums to darken your skin, and how to prevent it
  • Which vitamin C serums to try (and how to use them) to avoid this issue

How Vitamin C Protects Your Skin

Vitamin C serum darkens skin

Vitamin C scavenges free radicals and helps protect your skin from sun damage.

Truth be told, vitamin C is an ideal ingredient to use in the summertime, because that's when our skin is exposed to the most UV light—and therefore the most free radicals. 

Free radicals are toxic, unstable molecules that contribute to aging by depleting the natural antioxidants in our skin and causing cellular and DNA damage.

What vitamin C does, as an antioxidant, is:

  • Neutralize the oxidative stress caused by these free radicals
  • Protect against UV-induced skin damage 
  • Aid in skin repair

According to The Journal of Clinical and Aesthetic Dermatology, "sunscreens are only partially effective in blocking free radicals produced by UV exposure." (Shocking, right?!) So you should think of vitamin C as adding a secondary level of protection.

That's in addition to vitamin C's ability to brighten the skin, fade pigmentation, and (at least with L-ascorbic acid) promote collagen production!

What Causes Vitamin C to Darken Your Skin

Vitamin C serum darkens skin

An oxidized vitamin C serum (left) vs. a fresh vitamin C serum (right).

So, what's going on when a vitamin C serum makes your skin look darker?

There are two scenarios for why you might see a colour change, and both have to do with oxidation:

  1. The vitamin C has oxidized in the bottle
  2. The vitamin C has oxidized on the surface of your skin 

Here's what to know about each...

Vitamin C That Has Oxidized in the Bottle

Vitamin C serum darkens skin

An oxidized bottle of vitamin C (not only has the serum turned dark brown, but the rubber dropper has also started to dissolve).

After contact with light, heat and air, vitamin C eventually oxidizes and loses its potency. You'll know it when your serum changes colour, turning brown. (With L-ascorbic acid, this usually takes about three months after opening the bottle.)

The reason it can stain your skin is because vitamin C degrades into erythrulose—the EXACT ingredient you'll find in many self-tanners! Deciem, for example, uses erythrulose in Hylamide Glow Radiance Booster and The Chemistry Brand "Glow" Oil. A tan from erythrulose can last as long as a week!

Far more worrisome than an unwanted tan, however, is that erythrulose may even age your skin. As I explained in my article about self-tanner safety, erythrulose and dihydroxyacetone (DHA) darken the skin via the "Maillard reaction." Similar to caramelizing meat, this process generates free radicals and could accelerate sun damage and DNA damage—exactly what we're trying to avoid in the first place by using vitamin C!

[Read more about how self-tanners can age your skin]

Best case, you won't any get results from applying a vitamin C serum that has oxidized in the bottle. Worst case, it could not only cause colour changes, but also backfire in terms of skin repair! 

Vitamin C That Has Oxidized on Your Skin

Vitamin C serum darkens skin

A fresh bottle of vitamin C (notice the clear liquid with a thin consistency).

But what if you're using a fresh, non-oxidized bottle of vitamin C, and still notice a change in skin colour by the end of the day (or when you wake up in the morning, if you apply your C at night)?

According to Dr. Zoe Diana Draelos in Dermatology Times, "vitamin C preparations can also discolour on the skin surface as they contact oxygen in the environment. This accounts for the orange colour that may emerge on the skin in the morning after wearing a vitamin C preparation overnight."

How to Stop Vitamin C from Darkening Your Skin

Fortunately, there are a few things you can do to prevent oxidized vitamin C from staining (not to mention wreaking havoc on your skin goals!):

1. Prevent Your L-Ascorbic Acid Serum from Oxidizing

Drunk Elephant C-Firma Day Serum

Drunk Elephant C-Firma Day Serum

If you want to use a serum with L-ascorbic acid—the most proven and potent form of vitamin C—you need to be aware that it is highly unstable.

Ideally, look for L-ascorbic acid serums that also include ferulic acid and vitamin E, which will help stabilize the formula (not to mention double its photoprotection!). Some examples include:

It's important to use up your L-ascorbic acid serum as soon as you open it, within three months. 

Keep it away from light and heat (you may even want to store it in the fridge) with the lid tightly closed, and throw it away as soon as it changes colour or smells "off."

2. Switch to a Vitamin C Derivative

The Ordinary Ascorbyl Glucoside Solution 12 Percent

The Ordinary Ascorbyl Glucoside Solution 12%

Vitamin C derivatives are a good alternative to L-ascorbic acid because they are more stable and resistant to oxidation, so they're less prone to degrading and changing colour in the bottle (or on your skin!). They also tend to be gentler, due to their non-acidic pH levels.

Some of the best vitamin C derivatives include: 

While vitamin C derivatives are great for fighting free radicals and brightening, keep in mind that they're less proven than L-ascorbic acid in terms of increasing collagen.

3. Try Powdered L-Ascorbic Acid

True Botanicals Vitamin C Booster

True Botanicals Vitamin C Booster

If you don't want to miss out on the benefits of L-ascorbic acid, but need more stability than a liquid serum can offer, then consider a powder—a new option that gives you the best of both worlds!

Powdered L-ascorbic acid is much more stable than its liquid form, and less likely to degrade. To use it, you simply blend a small amount of powder into another serum or lotion, and apply the mixture to your skin. (For best results, each application should be mixed fresh.)

Some vitamin C powders to try include:

Vitamin C penetrates best at a low (acidic) pH, but this can also increase the risk of irritation to your skin. You might want to test your mixture with pH strips, aiming for a pH between 3.0 and 3.5.

4. Layer Oil Over Vitamin C Serum

MV Organic Skincare Pure Jojoba

MV Organic Skincare Pure Jojoba

If you struggle with vitamin C turning colour on your skin—even when it's applied from a fresh, non-oxidized bottle—consider pairing it with a face oil.

Apply the C first, and then a generous layer of oil on top of it. This should help create a bit of a barrier between the vitamin C and the oxygen in the air, which is responsible for it darkening your skin.

Look for thicker oils that will stay on top of the skin surface instead of sinking in, such as:

5. Wear Your Vitamin C Serum at Night

Slip Silk Sleep Mask

Slip Silk Sleep Mask

If you typically apply vitamin C in the morning, see if it helps to wear it at night instead. You'll still get protection from free radicals, but you won't be exposed to strong sunlight that can oxidize the formula on your skin. 

According to Dr. Joshua Zeichner, "your body builds up a storage of antioxidants as you use them, so using vitamin C serum at night will help guarantee your body has enough ready to go in the morning when you need them most."

6. Exfoliate Daily

COSRX BHA Blackhead Power Liquid

COSRX BHA Blackhead Power Liquid

If you've tried all of these things and STILL wake up with skin discolouration after using vitamin C, consider bumping up your exfoliation routine.

A gentle daily or even twice-daily acid exfoliation will slough off some of the dead skin cells that are stained by the erythrulose, helping to reveal your original lighter tone. 

Both alpha- and beta-hydroxy acids will accomplish this (although I prefer beta because they're strong but anti-inflammatory and non-photosensitizing). 

Here are a few acids to try:

[Read more about how to layer acids and vitamin C in a skincare routine]

Conclusion

The bottom line? You don't have to give up vitamin C if you want to avoid staining your skin. And you can absolutely still use it when you're getting sun exposure. You just need to be careful about oxidation!

If you're a detail-oriented type of person, monitoring your L-ascorbic acid for changes and keeping it away from light, air and heat probably won't be an issue.

But if you'd rather not deal with that, opt for an L-ascorbic acid powder or vitamin C derivative instead. That way, you've also got more time to finish up the product!

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