Vitamin C’s antioxidant properties also neutralize free radicals, molecules created by external factors like air pollution and sunlight, says Dr. Zeichner. Since free radicals speed up signs of aging, vitamin C helps address fine lines they cause, too. Think of it as the ideal daytime counterpart to the retinol or exfoliating acids you might use at night to smooth skin, speed up cellular turnover, and treat acne scars left over from breakouts.
Vitamin C can also inhibit your skin’s melanin production, which leads to discoloration like dark spots and hyperpigmentation, New York City-based board-certified dermatologist Patricia Wexler, MD, previously told Allure. Over time, she says, vitamin C can help prevent dark spots from forming in the first place so it looks glowy—in addition to evening out skin tone.
What to look for in vitamin C serums
Not all vitamin C serums are formulated equally—in fact, not even all forms of vitamin C are equal in effectiveness. Here are a few factors to consider when shopping:
Vitamin C comes in a nearly endless variety of forms, but ascorbic acid, also known as L-ascorbic acid, is the gold standard of vitamin C for its stability and efficacy. “Pure ascorbic acid has consistently been proven to be the most effective at penetrating the skin barrier,” says Dr. Wexler. Other dermatologist-approved forms of vitamin C you may come across in skin-care products include tetrahexyldecyl ascorbate, magnesium ascorbyl phosphate, and methylsilanol ascorbate.
Dr. Liu previously told Allure the average concentration of vitamin C in a skin-care formula is around 10% to 15%. Keep in mind that a higher concentration of vitamin C may lead to sensitivity, so sensitive skin types may want to stick to a lower percentage.
Antioxidants: You’ve probably noticed that vitamin C tends to be tag-teamed with two other antioxidants, vitamin E and ferulic acid, and there’s a reason for that. “Vitamin C effectiveness increases when combined with other antioxidants, such as vitamin E,” says Dr. Wexler. “Together, they can provide double protection against free-radical damage.”Humectants: Hydrating ingredients known as humectants, such as hyaluronic acid, glycerin, and squalane, partner well with vitamin C to boost hydration levels and ease the sting of the active ingredient, especially if you’re using a potent, high-percentage (above 15%) formula.Brightening ingredients: Niacinamide and tranexamic acid complement vitamin C in interfering with the pigment production process.Peptides: If you’re seeking firmer skin, peptides (which act as messengers between skin cells) can also help supplement vitamin C’s ability to dial up collagen production.
When to use vitamin C serum
Like most actives, dermatologists recommend slowly incorporating vitamin C into your skin-care routine to avoid irritation. Start with a few drops every two days, and, if your skin seems to tolerate it, you can work your way up to every day. We suggest applying vitamin C serums before your moisturizer and sunscreen in the morning to benefit the most from the antioxidant’s free-radical fighting power. If your skin can tolerate it, and if you want an overnight collagen boost, you can also apply it in the evening.
Meet the experts
Michelle Henry, MD, a board-certified dermatologist based in New York CityCarmen Castilla, MD, a board-certified dermatologist based in New York CityJenny Liu, MD, a board-certified dermatologist in Minneapolis and assistant professor at the University of MinnesotaPerry Romanowski, cosmetic chemistJennifer Gordon, MD, a board-certified dermatologist in Austin, Texas at Westlake DermatologyGretchen Frieling, MD, a board-certified dermatopathologist based in BostonTiffany Clay, MD, a board-certified dermatologist based in Atlanta, GeorgiaCaroline Robinson, MD, a board-certified dermatologist based in ChicagoJoshua Zeichner, MD, a board-certified dermatologist and director of cosmetic and clinical research at Mount Sinai’s Department of Dermatology in New York CityMona Gohara, MD, a board-certified dermatologist based in ConnecticutPatricia Wexler, MD, a board-certified dermatologist based in New York City
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When Allure tests a product, our editors look at it from every angle to best serve you. We review ingredients, scrutinize brand claims, and, when necessary, examine peer-reviewed scientific and medical studies. In addition to testing each and every product that’s included in every review, we rely on experts who shape their fields, including dermatology, cosmetic chemistry, and medicine, to help us vet the ingredients and formulas.
