Is vitamin C serum all it's cracked up to be? Benefits and what it does for your skin

Few things seem less sexy than vitamins and minerals. Tamper-proof green and yellow bottles and the smelly pills inside aren't the first things most people think of when it comes to looking young and beautiful. But the skin-care industry is busy pushing vitamin-C serums as an age-defying moisturizer anyway. And it seems to be working.

Amid the profits, advertising campaigns and viral success stories, industry executives seem to know they have something often in short supply in their market: actual science backing them up. At the same time, there are limits to what the topical nutrient can do – and plenty of words of caution as well.

How does vitamin C improve skin?

Vitamin C is an important nutrient used by one's body to form blood vessels, cartilage, muscle and collagen. It's commonly found in many foods and can be ingested as a pill or multivitamin supplement as well. Vitamin C can also be applied topically – usually in the form of a cream, moisturizer or serum.

Harvard Health Publishing, the media division of Harvard Medical School, notes that "Topical vitamin C is a science-backed, dermatologist-favorite ingredient that may help slow early skin aging, prevent sun damage, and improve the appearance of wrinkles, dark spots and acne." And because vitamin C is an antioxidant – meaning it fights toxins on the skin that come from air and other pollutants – it has rejuvenating and enhancing qualities as well.

Beyond potentially improving one's appearance, "Vitamin C has multiple other supportive functions to one's skin," says Kate Zeratsky, a registered dietitian nutritionist at Mayo Clinic in Rochester, MN. "These include stimulating collagen synthesis and wound healing, and assisting in antioxidant protection against UV-induced photodamage (sunlight)."

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What does vitamin C do for the face?

Despite such benefits, applying vitamin C as a topical cream – especially on one's face – should be done carefully. "As with any skincare product, it is crucial to understand the potential risks and precautions to ensure safe and effective use," says José Ordovás, PhD, a senior scientist of the Nutrition and Genomics Team at Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. For one thing, vitamin C is highly acidic, and has been known to irritate skin in some users.

Because of this, it's best to test a small area of any vitamin-C cream or serum on one's arm before applying it to one's face.

How much vitamin C can I apply safely to my skin?

In addition to exercising caution when applying vitamin-C serums to one's face, Ordovás says anyone with sensitive skin or allergies should be especially careful. "Some individuals may experience redness, stinging or itching when using high-concentration vitamin C products," he warns. To minimize risk, he recommends starting with a lower concentration serum, "between 5% and 10%," to make sure there isn't any reaction before buying higher concentrated levels.

Once allergies and sensitives have been checked, the serum or cream can be safely applied up to twice per day – generally in the morning and night after cleansing and toning. But there are still some caveats: "Another challenge with vitamin C serums is their inherent instability," says Ordovás. "Exposure to light, air and heat can cause the vitamin to oxidize, rendering it less effective and potentially harmful to the skin." To avoid this, he suggests choosing serums that are packaged in opaque, airtight containers and storing them in a cool, dark place.

Are some vitamin C serums better than others?

The skin-care market is an overly saturated one and there are seemingly endless vitamin-C serums to choose from. Though all advertise similar benefits, some brands are specifically formulated to provide enhanced levels of UV or toxin protection, or to work better with oily, hyperpigmented or acne-afflicted skin.

And in addition to the aforementioned dark, airtight containers Ordovás recommends, vitamin-C-serum consumers should also choose the L-ascorbic acid form of the product, and in concentration levels between 10% and 20%.

Regardless of the brand, it may also be wise to consider how best to use the serum alongside other topical products. "While vitamin C is generally considered safe for most skin types, using it with other active ingredients may increase the risk of irritation or reduce its effectiveness," says Ordovás. "To avoid issues, consider alternating vitamin C with other potent skincare ingredients and allowing your skin time to adjust and reap the benefits of each product."

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This article originally appeared on USA TODAY: What does vitamin C do for your skin? Serum benefits, risks explained