Does Using Vitamin C Boost Your Sunscreen?

As much as we love a good bulk buy, vitamin C isn't something to purchase in multiple quantities at once, according to Lortscher. It's notoriously unstable and degrades, thus losing effectiveness. An easy way to tell if your product has changed is if the color alters, typically to a yellowish tone.

You're also going to want to scan ingredient lists for "L-ascorbic acid" when picking up a vitamin C serum. "The only form of vitamin C that is a truly effective antioxidant and sun protectant is L-ascorbic acid," says Imber. "This is the true form of vitamin C." He states that most vitamin C is used as an additive in the ester form because it is easy to compound, however, it's marginally effective. Additionally, Imber cautions not to confuse sunscreens with added vitamin C with a vitamin C serum. The Youth Corridor Ultimate Antioxidant C Boost Serum, $195, lists "L-ascorbic acid" as an ingredient.

Another factor? Percentage. Gaul says that vitamin C is found to be most effective in the five percent to 20 prevent range with a pH of under 3.5. The Protocol Vitamin C Superserum, $72, has 10 percent ascorbic acid and a pH of 3.46. Imber says that 15 percent L-ascorbic acid is "the preferred concentration."

Buy now