What is vitamin C—and what does it do?

The better question is: What doesn’t vitamin C do? “Vitamin C is one of the most studied, potent, and plentiful antioxidants in human skin,” says Dr. Levin. “It continues to be one of the most recommended treatments for improving uneven skin tone, texture, acne scars, dullness, and fine lines.” But wait, there’s more! It also smooths wrinkles over time, thanks to its ability to boost collagen. No wonder every dermatologist is obsessed with it. Here’s the thing: sunlight, blue light, and just life in general creates oxidative stress, which plays a major role in aging, pigmentation, and inflammatory conditions like eczema and acne, as well as skin cancers. Antioxidants like vitamin C neutralize free radicals and aid in the skin’s natural rejuvenation process. The most common form of vitamin C you’ll find in skincare is L-ascorbic acid. As the most well-known form of vitamin C in the skincare game, it’s the most effective at penetrating the skin barrier and has great anti-aging benefits for most skin types. But there are also several vitamin C derivatives, such as tetrahexyldecyl ascorbate, ascorbyl palmitate, and sodium ascorbyl phosphate, among others. These derivatives are often combined with other ingredients to keep the vitamin C stable, triggering the release of pure vitamin C only when it comes into contact with the skin.

But isn’t sunscreen enough?

Well, not exactly. Without a doubt, sunscreen is key in order to maintain protection from sun damage, but your skin needs a little more. “Unfortunately, not only are people not applying enough or as often as they should, broad-spectrum sunscreen does not provide enough protection against other environmental stressors that cause free radicals, which is why the combination of antioxidants like vitamin C and sunscreen is ideal,” says Dr. Levin. “We now understand antioxidants are also important in order to neutralize free radicals from UV radiation, infrared radiation, and environmental stressors.” In other words, the best way to correct, treat, and prevent pigmentation is with a combination of both SPF and vitamin C.

Can you use vitamin C with acids or retinol products?

While vitamin C alone has proven benefits, studies show that combining it with equally potent ingredients can heighten its efficacy. “You can absolutely use Vitamin C, sunscreen, and retinol together!” says Dr. Levin. “While retinol is focused on accelerating skin cell turnover and repairing signs of aging such as fine lines, vitamin C improves skin protection from sun damage. If you have very sensitive skin and/or using vitamin C with other active ingredients, there are actually different types of vitamin C such as tetrahexyldecyl ascorbate that are less irritating and more stable, which is ideal for combination use with retinol.” If you’re new to vitamin C, here’s a heads-up: While budget-friendly vitamin C serums certainly do exist, the majority of formulas skew on the expensive side. “The best vitamin C formulations contain multi-tasking combinations that offer other skin-benefiting ingredients, such as humectants, retinol, sunscreen, peptides, and vitamin B3,” says Dr. Levin. That being said, they are totally worth the investment as a highly concentrated vitamin C serum will heal existing damage while warding off future inflammation. Below, some of the best vitamin C serums for every skin type and concern.