Jen is a writer for BuzzFeed based in New York.

Before we get into what they said, here's a little info about the experts I interviewed:

Dr. Dara Spearman is a board-certified dermatologist and founder of Radiant Dermatology Associates.

Dr. Dendy Engelman is a board-certified dermatologic surgeon at Shafer Clinic Fifth Avenue. 

Dr. Toral Vaidya, MD, MPH is a board-certified dermatologist at MDCS Dermatology.

Vitamin C serum is a topical skincare treatment that disperses a highly concentrated amount of the antioxidant to the skin. Not only does it help protect skin from environmental aggressors ike UV exposure and pollution, but it also boosts collagen production and brightens the complexion. In addition, it "improves the appearance of fine lines and uneven skin tone," and "supports overall skin health when used regularly," Dr. Engelman and Dr. Spearman said, respectively.

Dr. Vaidya explained the science behind it all: "Vitamin C inhibits an enzyme called tyrosinase, which is involved in melanin (pigment) production." She added that "by slowing this process, vitamin C can help prevent the formation of excess pigmentation." 

"Additionally," she continued, "as an antioxidant, it neutralizes environmental free radicals that contribute to skin aging, inflammation, and hyperpigmentation." 

One of the most popular forms of Vitamin C serum includes L-ascorbic acid, "which is the most studied and effective form of vitamin C," Dr. Spearman explained. "Ideally, it should be in the 10 to 20% range." 

However, it's worth mentioning that a higher percentage doesn't necessarily mean better efficacy. "Vitamin C works in a dose-dependent way up to a point," Dr. Engelman added. "After about 20%, you hit diminishing returns, and irritation risk climbs. Consistency is more important than chasing the highest concentration."

Dr. Vaidya added that outside of L-ascorbic acid, there are "vitamin C derivatives, which differ in potency and stability." She said that "L-ascorbic acid is more potent but less stable, whereas derivatives tend to be gentler and more chemically stable. Some skincare products also use plant-derived forms of vitamin C, which are generally gentler on the skin while still providing strong antioxidant benefits." 

The general consensus is that Vitamin C should be applied in the morning, after cleansing, but before moisturizer and sunscreen. Applying the serum early in the day is ideal because, according to Dr. Engelman, "it acts as an antioxidant shield against environmental stressors like UV rays and pollution throughout the day. While sunscreen protects from UV radiation, vitamin C helps neutralize the free radicals that still form, so they work beautifully together."

With consistent use, you might notice improvement in overall skin brightness and texture, including faded dark spots and greater radiance. According to all three doctors, results can be seen in as little as 8 to 13 weeks. 

Vitamin C serum works well for most skin types, however, those with sensitive skin or rosacea-prone skin should be careful. "In those cases, I may recommend starting with a lower percentage or using it every other day," Dr. Spearman said. "I always recommend patch testing, and it’s a good idea for any skin type!"

Dr. Vaidya added that for those with more sensitive skin, "it’s important to choose gentler formulations (with vitamin C derivatives) to minimize potential irritation."

"A common mistake I see is using too many actives alongside vitamin C," she explained. "It’s best to apply vitamin C at a separate time of day, or even on a different day, when incorporating other actives such as retinoids or exfoliants."

Dr. Althea's Vitamin C Boosting Serum ($24) and Dr. Althea's Gentle Vitamin C Serum ($24): "The Vitamin C Boosting Serum uses a 60% vitamin C‑rich Hippophae Rhamnoides Water and niacinamide, along with tranexamic acid to target dark spots," Dr. Vaidya said. "The Gentle Vitamin C Serum offers a sensitive‑skin‑friendly formula with niacinamide and 3‑O‑ethyl ascorbic acid, a vitamin C derivative. Both are lightweight, absorb easily, and are designed to improve overall skin clarity with regular use." 

Maelove’s Glow Maker ($33): Dr. Spearman recommends this as "a more affordable option." She said, "It's a solid choice with a similar antioxidant profile." 

La Roche-Posay Pure 12% Vitamin C Serum ($45): "This is a great multitasker," Dr. Engelman explained. "It brightens and hydrates the skin, reduces the look of fine lines and wrinkles, and smoothes texture, to make your skin look more radiant and glowy."

Pareva Beauty C35.5 Firming Glow Serum ($74): Dr. Spearman recommends this as it "combines 30% tetrahexyldecyl ascorbate (THD), an oil-soluble form of Vitamin C that is more stable and is powered by Molecur 3." She explained that "Molecur 3 is the brand's proprietary technology that targets exosomes, energizes skin through NAD+, and decreases inflammation, making it a good option for patients focused on preventing future aging for firmer, brighter looking skin." 

IMAGE Skincare VITAL C Anti-Aging Serum ($91): "The antioxidant blend in the formula helps neutralize daily damage from things like pollution and UV exposure, while also providing a more luminous and smooth texture, all while still being gentle on the skin," Dr. Engelman said.

Vivier Serum 10 ($108): "This is a great option for those newer to Vitamin C serums," Dr. Engelman said, adding, "it uses L-Ascorbic Acid USP, a bio-available form of Vitamin C, which delivers in a unique patented system to reduce the chances of irritation." 

SkinCeuticals’ C E Ferulic ($185) or Phloretin CF ($185): Simply put, Dr. Spearman said, "[these products] have stabilized formulas with strong antioxidant combinations."