Vitamin C Serums 101: Best Products, Benefits, Side Effects, and More

You reach for vitamin C when you feel a cold coming on, but did you know it can also deliver a smooth, glowing complexion? In recent years, vitamin C has become a holy-grail item for the skin-obsessed.

“Vitamin C is a hot topic, and it is buzzworthy, because it has so many preventive and maintenance benefits,” says Nazanin Saedi, MD, a board-certified dermatologist and a clinical associate professor at Thomas Jefferson University in Philadelphia.

Here, we dive into everything you need to know about vitamin C serums, including why to use one, how to apply it, and what to watch out for.

A vitamin C serum is a skin-care product packed with vitamin C. It has the consistency of a liquid or gel, and is applied topically to the skin. You’ll find these serums wherever you normally purchase skin-care products — at department stores, beauty stores, and some drugstores, too. On the packaging, you’ll likely see words touting skin benefits like “firming,” “brightening,” and “collagen boosting.” People add vitamin C serum to their skin-care routines to tap into those benefits.

“The benefit of vitamin C is it’s an antioxidant, so it helps prevent the forming of free radicals, which go on to break down collagen and elastin,” Dr. Saedi says. The result, she says, is glowing, youthful skin.

Great, right? By now you may be thinking about how to increase vitamin C in your diet to reap these benefits. Unfortunately, simply eating more oranges and cantaloupe isn’t going to cut it. That’s because the epidermis, the outermost layer of the skin, doesn’t have blood vessels to send nutrients to the skin cells, research notes.

Vitamin C can, however, be applied topically — and that’s where vitamin C serums come in. “Vitamin C is best known for its ability to neutralize free radicals and improve aging skin,” says Joel Schlessinger, MD, a dermatologic surgeon in Omaha, Nebraska. “It can also improve collagen and elastin synthesis — which can improve the appearance of fine lines and wrinkles; help reduce inflammation, provide natural, mild exfoliation; and brighten skin.”

Saedi recommends vitamin C serums for people of all ages because virtually everyone is at risk of sun damage, and with vitamin C serums “we are minimizing the amount of sun damage that our skin’s getting from sunlight,” she says. She says it does double duty, both protecting the skin and helping problem areas recover. “It’s preventive in that it’s protecting you from sun damage and signs of aging like wrinkles,” Saedi says. “It also helps promote collagen and boost your natural collagen formation.”

Saedi says to apply a few drops of serum to your face after you wash and dry it. “A little bit goes a really long way,” she says. She recommends putting it on every morning, all year round. “It has some benefits with sun exposure, so it helps to apply it in the morning as the first layer of protection,” she says. She says to then layer on your moisturizer and sunscreen. Serums are better than drops of vitamin C “boosters” added to your moisturizer, Saedi says. Vitamin C drops may not be as potent as serums, and mixing them with moisturizer may dilute the effects.

Store your bottle in a cool, dark place away from extreme heat, such as a bathroom cabinet, as opposed to on your counter. “Storing a vitamin C serum correctly is integral to its success,” Schlessinger says. “A good rule of thumb is to toss the serum six months after it’s been opened and to keep the serum in a cool, dark place.” If you’re using it according to the instructions, it’ll likely be gone before the six months is up. If not, you’ll want to throw it out. “When vitamin C is used past its shelf life, it can actually have negative effects,” Schlessinger says. More on that next.

Vitamin C is a safe and generally well-tolerated ingredient. “The only risk is that some of these serums have so many different ingredients in them,” Saedi says, adding that these extra ingredients may result in an allergic reaction in some people.

SkinBetter Science Alto Defense Serum ($160, Skinbetter.com) stars vitamins C and E, along with 17 antioxidants to guard against a range of free radicals and reduce redness.

Drunk Elephant C-Firma Day Serum ($78, Sephora.com) contains 15 percent L-ascorbic acid, plus ferulic acid for a powerful yet lightweight day serum.

Paula’s Choice C15 Super Booster ($52, Dermstore.com) is another high-potency pick with 15 percent vitamin C, along with E and ferulic acid, plus hyaluronic acid to attract moisture for supple skin.

Vichy Vitamin C Serum Brightening Skin Corrector ($22.89, Walgreens.com) boasts minimal ingredients to keep things simple. With ascorbic acid, vitamin E, and hyaluronic acid, this serum may boost skin smoothness and radiance.

The Ordinary Ascorbic Acid 8% + Alpha Arbutin 2% ($11, Deciem.com) offers a budget-friendly way to try a vitamin C serum, and also contains alpha-arbutin, another ingredient that’s touted for its skin-brightening abilities.

Additional reporting by Jessica Migala.