When most people think about sun protection, they think of sunscreen—and for good reason. Sunscreen is the cornerstone of preventing UV damage, skin cancer, and premature aging. But what many people don't realize is that another skincare ingredient has an important supporting role: Vitamin C.
Before you toss your sunscreen aside, let's be clear: Vitamin C is not sunscreen. It doesn't absorb or block ultraviolet (UV) radiation, and it should never replace your daily SPF. Instead, Vitamin C protects your skin in an entirely different way—through chemistry.
When ultraviolet light reaches your skin, it does more than simply cause a sunburn. UV photons carry enough energy to trigger a series of chemical reactions inside skin cells. One of the most important is the formation of reactive oxygen species (ROS), commonly known as free radicals.
Free radicals are highly unstable molecules with unpaired electrons. Because they are chemically unstable, they seek stability by stealing electrons from nearby molecules. Unfortunately, those nearby molecules include collagen, elastin, cell membranes, proteins, and even DNA.
This chain reaction is known as oxidative stress, and it is one of the primary drivers of photoaging. Over time, oxidative stress contributes to wrinkles, loss of elasticity, uneven pigmentation, chronic inflammation, and the accumulation of DNA damage associated with skin cancer.
This is where Vitamin C becomes so fascinating.
Vitamin C, or ascorbic acid, is one of the body's most important antioxidants. Chemically, it functions as what's called a reducing agent, meaning it readily donates electrons to other molecules. Instead of allowing free radicals to steal electrons from your collagen or DNA, Vitamin C donates one of its own. By doing so, it neutralizes these reactive molecules before they can damage healthy skin.
In a sense, Vitamin C sacrifices itself to protect your skin. That's the very definition of an antioxidant.
This is also why sunscreen and Vitamin C aren't competitors—they're teammates. Sunscreen works by reducing the amount of UV radiation that reaches your skin in the first place, while Vitamin C helps neutralize the oxidative stress caused by the UV radiation that inevitably gets through. No sunscreen blocks 100% of ultraviolet light, which is why dermatologists often recommend pairing sunscreen with topical antioxidants as part of a comprehensive morning skincare routine.
Vitamin C's benefits don't stop there. It's also essential for making healthy collagen. Your body requires Vitamin C as a cofactor for two enzymes—prolyl hydroxylase and lysyl hydroxylase—that stabilize newly formed collagen fibers through hydroxylation of proline and lysine residues. Without adequate Vitamin C, collagen becomes weaker and less organized. In fact, the classic symptoms of scurvy—poor wound healing, bleeding gums, and fragile skin—are all consequences of defective collagen production due to Vitamin C deficiency.
Of course, not all Vitamin C products are created equal. The most extensively studied form, L-ascorbic acid, is highly effective but notoriously unstable. Exposure to oxygen, heat, or light causes it to oxidize, which is why many Vitamin C serums gradually turn yellow or brown over time. Once oxidized, it becomes far less effective.
For this reason, researchers have developed more stable Vitamin C derivatives. At Vetted Dermlab, we chose tetrahexyldecyl ascorbate (THD), an oil-soluble derivative that offers excellent stability and penetrates the lipid-rich outer layers of the skin efficiently. Once absorbed, it is converted enzymatically into active Vitamin C, allowing antioxidant activity while avoiding many of the formulation challenges associated with L-ascorbic acid.
We also paired THD with ergothioneine, a remarkable antioxidant that has attracted growing interest in dermatology because of its exceptional stability and its ability to accumulate in tissues exposed to oxidative stress. Rather than relying on a single antioxidant, we believe supporting the skin's natural antioxidant network offers a more thoughtful approach to daily photoprotection.
The take-home message is simple: sun protection isn't just about blocking UV rays. It's also about helping your skin respond to the oxidative stress that UV exposure creates. Sunscreen and Vitamin C accomplish these goals through entirely different mechanisms, which is why they work so well together.
So yes, Vitamin C does help protect your skin from the sun—but not because it acts like sunscreen. Instead, it helps defend your skin at the molecular level, neutralizing the free radicals that contribute to aging and skin damage. That's chemistry worth understanding—and one more reason Vitamin C remains one of our favorite ingredients for healthy skin, every day of the year.
