Vitamin C Serum: Benefits, Side Effects, and Beyond

Want to address everything from wrinkles and fine lines to hyperpigmentation in a single step? Then allow us to introduce you to vitamin C serum, the MVP of the skincare world.

Lest you confuse this for another trend that’s high in buzz and low in science, good news: There’s more than enough evidence to back up the many, many vitamin C serum benefits — which explains its staying power. In fact, says NakedPoppy research scientist Marisa Plescia, “vitamin C is one of the most studied antioxidants in skincare.”

Since it’s very much a treatment-focused ingredient, you’ll often find it as a vitamin C serum — understandably. “Serums are potent formulations with higher concentrations of actives,” says NakedPoppy skin specialist Tara Parenti. But how, exactly, might a vitamin C serum benefit your skin? Glad you asked — here are the deets.

What does vitamin C serum do for the skin?

Vitamin C serum benefits are plentiful, which is part of the reason it’s such a key player for so many skin types and concerns. For starters, it’s an antioxidant, which “is a potent compound that helps fight free radicals in your body and help prevent or slow damage to the cell caused by oxidative stress,” says Plescia.

That’s kind of a big deal, as free radicals are highly unstable molecules that can accelerate skin aging, especially extrinsic skin aging — in other words, skin aging caused by environmental factors. These destructive little molecules can be naturally formed in your body (just a side effect of being alive!) as well as from those environmental factors, including UV exposure, ozone, cigarette smoke, and even pollution. Enter vitamin C, which shuts that all down.

And, as an antioxidant, it also offers synergistic benefits when paired with certain products. For example, “it actually pairs well with SPF to increase protection from UV rays,” says Parenti. If your sunscreen is your first line of defense against UV rays, then vitamin C is there to run interference on any free radicals that sneak through.

On top of that, “vitamin C has many other skin advantages, such as encouraging collagen production and helping to fade dark spots and other skin hyperpigmentation,” says Plescia. Let’s break it down:

How vitamin C serum benefits wrinkles

Vitamin C doesn’t just work in one way to lessen the appearance of fine lines and wrinkles. (That would be too easy.) Rather, it has a two-pronged method of keeping skin firm and bouncy.

For starters, “as a photoprotective ingredient, vitamin C has been shown to inhibit the activation of the protein AP-1, which can help reduce collagen damage from UV exposure. [1],” says Plescia. In dampening this protein, vitamin C halts a domino effect that could otherwise lead to both collagen degradation and reduced collagen production. In fact, says Plescia, “one controlled study found that using 10% topical vitamin C over a 12-week period showed a reduction in photoaged scores and improvement in wrinkling in vitamin C-treated patients as compared to placebo. [2]” 

Then, there’s the second advantage: It can help keep collagen production running smoothly. “Vitamin C also has an intrinsic skin-smoothing effect, as it directly activates and helps regulate the factors involved in collagen synthesis,” says Plescia.

How vitamin C serum benefits dark spots and dullness

Vitamin C can also offer major perks on the skin tone front, addressing hyperpigmentation (such as dark spots) and promoting overall brightness. “Studies have found that vitamin C helps inhibit the tyrosinase—the main enzyme responsible for the production of melanin—thereby helping decrease pigment formation,” says Plescia. “A clinical study examining the effect of a topical formulation containing 25-percent vitamin C and with a penetration enhancer reported a significant decrease in pigmentation caused by melasma after 16 weeks. [3]” 

Brighter, more even-toned skin? We’re in.

Is vitamin C clean?

Vitamin C itself can be considered a clean ingredient in all forms, be it ascorbic acid or tetrahexyldecyl-ascorbate. As is the case with retinol, the concern is more about the ingredients it’s paired with in a given formula, such as polyethylene glycol (a petroleum-derived compound) and BHT and BHA, two preservatives. Shop from a retailer with clean beauty standards to ensure your vitamin C serum is free of concerning ingredients.

Can I use vitamin C serum everyday?

Yes, you can and should use vitamin C daily. “Studies show that excessive exposure to UV light or pollutants may lower vitamin C concentration in the skin, which makes topical vitamin C great for daily use [4],” says Plescia.

Plus, as with most skincare ingredients, consistency is key to both A) seeing results, and b) reaping the max amount of benefits. Consider using it both morning and night, since each strategic timing can offer two distinct advantages.

Applied in the A.M., “vitamin C is a great source of extra protection from UV and other environmental exposure during the day, especially when layered with SPF,” says Plescia. As we mentioned earlier, it basically acts as a back-up to your sunscreen to give your skin the most possible protection.

At night, on the other hand, your skin *finally* gets a break from all the environmental aggressors of the day — sunlight, pollution, that sort of thing — and starts working to repair that damage, which is where vitamin C comes in. In fact, studies have shown that repair of DNA-damaged skin cells from UV radiation peaks at night. [5] “Strong antioxidants, such as vitamin C, are noted to help repair DNA damage and protect against reactive oxidative species after UV exposure [6],” says Plescia. “Since at night the skin is already at its peak of repair from environmental aggressors, adding vitamin C will only add and further strengthen the protection against oxidative damage.”

Does vitamin C serum have side effects?

Vitamin C serum side effects are relatively mild, but as with many things in life, anything is possible. “Those with sensitive and reactive skin or could experience redness from vitamin C, since it’s highly acidic and has to be at a lower pH in order to be effective,” says Parenti.

Not only that, but “for some, vitamin C can be very sensitizing,” she says. “Always do a patch test behind your ear as this is the closest skin to the neck.” (Sensitizing means that while your skin may not be inherently sensitive, it becomes sensitized if habits like over-cleansing or harsh products strip the skin barrier.)  If you notice any redness or discomfort, you can still get the vitamin C serum benefits. Just opt for a product with a lower percentage or seek out an oil-soluble derivative of it, such as tetrahexyldecyl ascorbate. (For context, says Plescia, most concentrations of vitamin C are in the range of 10 to 20 percent.)

How to use vitamin C serum

In most cases, you can find vitamin C in a serum — which, as we noted above, is considered the ideal delivery mode. Plus, “with the issues of stability surrounding vitamin C, serums can be better formulated to cater to these stability issues and are often found in sizes that can be used more quickly than other cosmetic products,” says Plescia.

Maya Chia’s The Super Lift Vitamin C-More Treatment features three forms of vitamin C, including tetrahexyldecyl ascorbate, in its shelf-stable formula. (Psst: It also doubles as a primer, as it’s clinically proven to help extend makeup’s wear.) 

To round out the rest of your routine, take the 3-min NakedPoppy assessment, which will automatically match you with the ideal skincare products for your individual skin type and concerns.

Use it after cleansing and toning (if you so choose). Once it’s fully absorbed into skin, follow up with moisturizer and, if it’s daytime, sunscreen. With daily use, you should start to see results in 12 to 16 weeks (worth the wait!).

Once you apply it, make sure to store it properly, which can help with stability. “Vitamin C should be kept airtight in a dark, cool space,” says Plescia. “If the color of the serum becomes dark — usually brown — or becomes cloudy and has a rancid odor, this most likely means that the vitamin C has oxidized and will be less effective.”

Chances are, though, that you’ll get through your vitamin C serum long before this happens — and see the incredible results for yourself.

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