While skin care ingredients promising to erase fine lines, ward off wrinkles, and fade away dark spots are a dime a dozen, there are a few out there that can actually make a huge difference in the look and feel of your skin. Case in point? Vitamin C.From neutralizing free radicals to brightening your complexion, vitamin C can be a game changer in your skin care routine. But, when is the best time to incorporate it into your regimen and how can you reap the most reward? Let’s just say, if you aren’t using a daily vitamin C-formulated product in your 20s, you’re missing out. The Benefits of Vitamin CA potent antioxidant, vitamin C has been considered a gold standard anti-aging ingredient by dermatologists for ages. Found in everything from concentrates to serums to face masks, vitamin C-formulated skin care products are known to help neutralize free radical damage to the skin’s surface.Free radicals—found in the atmosphere and created by everything from pollution to UV rays—can affect the skin in a number of ways. Of all the ways free radicals affect the look and feel of our complexion, premature signs of aging skin rank at the top.Since vitamin C helps to neutralize free radicals, it can be a great line of defense against the first signs of aging. What’s more, vitamin C-formulated products have been shown to help achieve glowing skin and a more even-toned, even-textured complexion. When to Use Vitamin CIf you thought all your skin needed in your 20s was a makeup wipe, some moisturizer, and a little SPF, think again. It’s during our 20s that the some of the skin’s natural processes—the ones that keep our skin looking youthful—start to decline. And, while you may not see the effects of this until you reach your 30s, it doesn’t mean you should wait to start addressing them.In fact, it’s in your early 20s that you should be reaching for a gold-standard antioxidant like vitamin C in order to help to counteract some of the visible effects of the aging process. Using a vitamin C concentrate or serum like Kiehl’s Powerful-Strength Line-Reducing Concentrate as early as your 20s can make a marked difference in the appearance of your skin, helping to ward off those signs of premature skin aging before they make their appearance. Along with broad-spectrum SPF—which you should be using each and every day—vitamin C products are key in helping you look younger, longer.How to Use Vitamin CPowerful-Strength Line-Reducing Concentrate, specifically, has a powerful formula—as its name suggests—boasting 12.5 percent vitamin C. It comes in dark packaging, which dermatologists frequently recommend since vitamin C can break down when exposed to light.While many vitamin C-formulated products are only used in the morning, Kiehl’s Powerful-Strength Line-Reducing Concentrate should be used morning and night. First, cleanse your skin thoroughly. Next, apply the vitamin C serum all over your face (avoiding the eye area and extending a little love to your neck). Finally, in the morning layer the product underneath your sunscreen to have the ultimate defense against environmental aggressors and at night use a hydrating night cream to lock in moisture.Kiehl’s Powerful-Strength Line-Reducing Concentrate, $62 MSRP