For brightening up a dull complexion and erasing sun spots, vitamin C is the gold standard of ingredients, especially as the years go on. As such, getting familiar with the powerhouse antioxidant is essential for any robust skincare strategy.

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“Vitamin C is perhaps the most potent topical antioxidant we have,” explains dermatologist Joshua Zeichner, M.D., of the natural collagen booster. “It neutralizes free radical damage and protects the skin against UV light and other environmental aggressors, as well as blocking abnormal production of pigmentation to even skin tone and fade dark spots.”

And while it’s best known for brightening, it can also be instrumental in skin firming, adds Los Angeles super facialist Kate Somerville. “I have used vitamin C in my clinic for years to help with elasticity and tighten the skin around the neck and décolletage,” she says.

Here, how best to utilize the hero ingredient for a brighter, smoother, and plumper complexion year-round.

Choose the Right Concentration

Identifying the right concentration for your skin type is essential to how effective your topical vitamin C will be, says New York City dermatologist Dr. Patricia Wexler.

“Begin with a low concentration of 10% and increase to 15% or 20% as tolerated,” she instructs. For oily or normal skin, L-ascorbic acid is the most potent form of vitamin C and can be the most beneficial, while for dry and sensitive skin, magnesium ascorbyl phosphate, a water-soluble vitamin C, is less irritating.

Pay Attention to pH

Absorption of a vitamin C is largely contingent on its pH level. If you have normal skin, look for one with a low pH of approximately 3.5 for optimal absorption. If you have sensitive skin, you should use a formula with a pH of 5 to 6. “This is the skin’s natural pH and will not be as irritating,” says Wexler.

Go With a Serum

Designed to deliver a high concentration of actives, serums are the most common form of delivery for vitamin C. “They keep that ingredient stable and enhance penetration through the outer skin layer,” says Zeichner. As far as complementary ingredients are concerned, Wexler believes vitamin C works best in combination with vitamin E, ferulic Acid, vitamin B, and hyaluronic acid.

“Vitamin C and E are both antioxidants and support each other,” she explains, adding that ferulic acid is another antioxidant which boosts and stabilizes both vitamin C and vitamin E in fighting free radical damage and collagen production. That being said, sensitive skin types might benefit from mixing their serum into a moisturizer, or opting for a vitamin C-infused moisturizer for gentler delivery.

Start Slowly

To keep skin happy, take a gradual approach when adding vitamin C to your regimen. “With any active, it’s important to start slowly when incorporating ingredients into your routine,” says Somerville. “I’ve seen some amazing results with clients who’ve added vitamin C into their regimen at three times a week and worked up to daily use.”

To that end, don’t expect instant gratification. “It takes several weeks of continuous use to start to see improvement in skin tone,” says Zeichner, adding that because it’s a key ingredient for prevention, some benefits will be imperceptible.

Store It Safely

Vitamin C serums come in two broad categories: Water-based and anhydrous (which literally means “without water”). The former is more unstable and light-sensitive, and is typically held in opaque or amber colored bottles for that reason, while the latter tends to be more stable, even in the presence of sunlight.

No matter what kind you opt for, ensuring your vitamin C is stabilized and kept airtight in a dark, cool space is essential. “If the color becomes dark or cloudy it has already oxidized,” cautions Wexler, adding that the same is true if you detect a rancid odor.

Layer It Under SPF

Unlike hydroxy acids or retinol, vitamin C does not make the skin more vulnerable to sunburn. That being said, the most potent forms of vitamin C are vulnerable to light exposure, and therefore the use of vitamin C must be in conjunction with broad-spectrum UVA/UVB coverage.

The good news is that, when layered underneath sunscreen with a minimum of SPF 30, vitamin C protects the skin even further. “Think of it as a safety net to help neutralize free radical damage that can occur from UV light penetration despite our best protection efforts with sunscreen,” says Zeichner.

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