What Every Derm Wants You to Know About Vitamin C (and Why Yours Might Not Be Working)

“What have you been doing with your skin?”

There are very few products that prompt this kind of reaction—unprompted, admiring, slightly suspicious. But vitamin C is one of them. Especially in its most active form, L-ascorbic acid, it’s the kind of ingredient that makes skin look so clear and radiant, it practically invites follow-up questions. The list of benefits is long: It brightens, firms, softens fine lines, and evens tone—whether skin runs dry, oily, sensitive, or somewhere in between. Perhaps most importantly, vitamin C makes you absolutely glow. Use it once and see instant results, but keep at it and your skin will start to look like it spends every evening in a cryotherapy chamber.

“It’s a powerful antioxidant that can help build collagen and soften the look of dark spots,” says New Jersey dermatologist Jeanine Downie, MD. Almost all antioxidants can help limit the formation of free radicals in the skin caused by the sun or pollution; topical vitamin C has been shown in studies to have a mild sun-protective effect, too (though it’s no substitute for sunscreen). And because it’s mildly exfoliating, vitamin C can help even skin tone and brighten it, which is helpful for people with hyperpigmentation. “Used regularly, it can also help decrease the appearance of fine lines and wrinkles,” says Downie. You can use vitamin C every morning or evening (or both).

But the catch with L-ascorbic acid has always been stability. The ingredient is highly reactive—exposure to water, light, or air causes it to degrade, turning the formula brown and stripping it of potency. Even the best conventional preservatives can’t fully prevent vitamin C from oxidizing, which is why stability is such a crucial focus in modern skin-care formulas.

At goop, that challenge is even greater: We don’t use toxic preservatives or stabilizers—only ingredients that meet our clean standards. So when we develop or sell any vitamin C product, it has to check three boxes: it must be clean, it must be potent, and it must stay stable long enough to actually work.

Our own goop Beauty serum does this by separating the pure L-ascorbic acid powder from the liquid until the moment you activate it—so the vitamin C stays powerful and fresh for the full three-month supply.

While our formula is a gold standard, it’s not the only one. The following vitamin C products all meet goop's rigorous criteria: They are clean, stable, and so effective your partner will probably try to steal them.

goop Beauty20% Vitamin C+ Advanced Brightening Serum$125.00SHOP NOW

Clean, Shelf-Stable Vitamin C Treatments That Really Work

WHERE VITAMIN C FITS IN YOUR ROUTINE

In general, vitamin C should go on bare skin as a first layer, right after cleansing. Wait a few minutes after you smooth it on, then, if you need more hydration (many skin types will), apply a nourishing oil or moisturizer. To supercharge both the vitamin C and the ingredients in your moisturizer, the Depuffing Wand from Theraface is pretty incredible: Choose from heat, cold, or contrast therapy and glide it over your face: The heat helps boost circulation, cold depuffs and minimizes the look of pores, and contrast therapy delivers first heat, then cold, to amplify your radiant results. (It also happens to feel amazing).

THE MOST IMPORTANT STEP: MINERAL SUNSCREEN

If you want any of your results—from your vitamin C or the treatments you apply afterward—to last, preventing sun damage is absolutely critical. Truly, there is no more powerful youth-boosting cream on the planet than sunscreen.

BONUS: FOR YOUR BODY