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
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
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:
- The vitamin C has oxidized in the bottle
- 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
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 self-tanner tutorial, 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
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!):
Prevent Your L-Ascorbic Acid Serum from Oxidizing
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:
- SkinCeuticals C E Ferulic
- Timeless 20% C + E + Ferulic Acid Serum
- Drunk Elephant C-Firma Day Serum
- Paula's Choice C15 Super Booster
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."
Switch to a Vitamin C Derivative
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:
- Magnesium ascorbyl phosphate (MAP), found in Skin Inc Supplement Bar Vitamin C Serum and Youth to the People Superfood Firm and Brighten Serum
- Sodium ascorbyl phosphate (SAP), found in Mad Hippie Vitamin C Serum
- Ascorbyl glucoside, found in The Ordinary Ascorbyl Glucoside Solution 12%
- Ethyl ascorbic acid, found in Hylamide C25 Stabilized Vitamin C Booster
- Ascorbyl tetraisopalmitate, found in Joanna Vargas Rescue Serum
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.
Try Powdered L-Ascorbic Acid
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:
- The Ordinary 100% L-Ascorbic Acid Powder
- True Botanicals Vitamin C Booster
- Good Molecules Vitamin C Booster Powder
- Philosophy Turbo Booster C Powder
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.
Layer Oil Over Vitamin C Serum
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:
- Herbivore Orchid Facial Oil
- RMS Beauty Raw Coconut Cream
- Drunk Elephant Virgin Marula Luxury Face Oil
- MV Organic Skincare Pure Jojoba
Wear Your Vitamin C Serum at Night
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."
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:
- COSRX BHA Blackhead Power Liquid
- Paula's Choice Skin Perfecting 2% BHA Liquid Exfoliant
- COSRX AHA 7 Whitehead Power Liquid
- Tarte Knockout Tingling Treatment
[Read more about how to layer acids and vitamin C]
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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