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1 week ago
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Of the many trendy anti-aging skin-care ingredients on the market today, vitamin C is among the few that dermatologists and skin-care researchers agree actually works. Sounds great, right? Well, there's a catch. While effective, vitamin C is also an unstable molecule that requires lots of care to retain its potency in skin products. Because of this, quality vitamin C serums tend to be pricey — sometimes shockingly so. But there's an exception: CosRx The Vitamin C 13% Serum, on sale for a jaw-dropping $15 during Amazon's Presidents' Day sale.
CosRx's potent vitamin C serum contains 13% of the hero ingredient in the form of L-ascorbic acid, the only vitamin C derivative clinically proven to brighten and smooth skin.
Why is it a good deal? 💰
CosRx is a trusted K-beauty brand known for its high-quality ingredients, and its product potency and efficacy. (If you haven't tried its bestselling snail mucin, check out my review.) True to form, this serum is made with 13% pure L-ascorbic acid, clinically proven to help brighten and tighten skin, stimulate collagen production and lighten dark spots. It also contains vitamin E, which studies show boosts vitamin C's efficacy; and hyaluronic acid, which hydrates and helps plump drier, mature skin.
Given this all-star ingredient lineup, $21 is already a good deal, but at $15, this is an absolute steal. How much of a steal, you ask? Well, the longtime gold standard vitamin C serum, cult-favorite C E Ferulic from SkinCeuticals, will set you back at least $182 for just 1 ounce. Drunk Elephant's version, my pick for best vitamin C serum of 2025, is just shy of $80.
Why do I need this? 🤔
Vitamin C is a face- and neck-saver if your complexion is looking dull, sallow or drab; if you have brown spots from sun damage; or if your skin is just less bouncy and full of life than you'd like. And its benefits have been extensively researched, unlike many other skin-care ingredients.
"A vitamin C serum is nonnegotiable. You need it twice a day," says facial plastic surgeon Dr. Kay Durairaj. "In the morning, it's an antioxidant to treat sun damage; in the evenings, it's going to help build collagen and repair your skin." Studies show that daily use of vitamin C improves skin texture, brightens skin tone, reduces hyperpigmentation and dark spots from sun damage and diminishes redness, particularly if the formula has a concentration of 10-20% vitamin C. Moreover, it works relatively quickly, often in as little as three months.
CosRx's vitamin C serum brightens and tightens skin as effectively as luxury brands, but at a fraction of the cost. (Amazon)
What reviewers say 💬
Customers agree that this serum helps brighten and tighten their skin, and they especially love the speed of the results.
Pros 👍
"FINALLY an effective serum, best I've used," said one happy shopper. "I had discoloration, but my skin is much more even-toned now. No vitamin C serum improved my skin before this — I used vitamin C serums just because you're 'supposed' to — but this one works."
"I'm on the fifth day of using this and I can't believe it. I can see a difference," explained another satisfied customer. "My skin is brighter and softer in just a few days. I've never with any other skin product seen results so quickly. I do believe I've finally found a good vitamin c serum that I'm gonna stick with."
Other users were surprised to find the formula works even for sensitive skin: "A solid addition to my skin-care routine," said this reviewer. "My skin feels hydrated and plump after using this. It's not sticky or heavy, which is great. Also, I have pretty sensitive skin, but this serum didn't cause any irritation or redness, which is a win for me when it comes to Vitamin C products."
Cons 👎
The biggest complaint about CosRx's vitamin C serum is the scent — which, like many products of its kind (even the most expensive) is funky and sulfurous. Others found fault with the sticky texture.
"Smell is gross," grumbled one user (who still couldn't deny the results). "It smells like wet dog food, but feels great on the skin and it's brightened my skin so far."
"It is VERY sticky," said another. "The consistency is thick and gooey. And it leaves your face very, very sticky."
A skin-care product that does what it says it will do at an affordable price? That's what we call a unicorn, folks.
Other CosRx products we recommend:
My beloved snail mucin from CosRx is excellent for evening skin tone and making your face look softer and brighter overall. It's won multiple awards, has over 56,000 five-star Amazon reviews and impresses most beauty editors I know.
After using it the first time, my face was noticeably dewier, and other users have boasted about its ability to hydrate, repair and improve dullness in the skin — all of which helps wrinkles look less deep and crepey. When I tried it again after a medi-spa laser treatment, I found it soothed and calmed my skin as it healed, lending a healthy sheen.
If I could, I'd buy every person I know a bottle of the aforementioned snail serum — it's truly one of the most effective skin-care items for complexion smoothing, skin softening and dark-spot lightening I've ever tried. But, because handing over a bottle of snail mucus might seem a wee bit strange, these sheet masks are a quality alternative.
They contain the award-winning snail slime, are highly hydrating and work for most any skin type. Users report that they help with skin inflammation and even rosacea, and this pack of 10 is a solid entry point into the famous K-beauty line.
If your skin isn't sensitive (or you've been using vitamin C for a long time), this intensified vitamin C serum contains 23% L-ascorbic acid for a deeper glow up.
If you have Amazon Prime, you'll get free shipping, of course. Not yet a member? No problem. You can sign up for your free 30-day trial here. (And by the way, those without Prime still get free shipping on orders of $35 or more.)
The reviews quoted above reflect the most recent versions at the time of publication.
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