The Vitamin C 23 Serum — Reddit Reviews
by COSRX
Updated September 3, 2026
23% pure vitamin C serum with strong brightening but frequent irritation reports.
What the community says
This high-strength serum offers potent brightening and dark spot fading benefits, favored in K-beauty circles. It requires refrigeration and has a short shelf life to prevent oxidation. Many find it too harsh for sensitive or dry skin, often causing stinging or redness.
What this means for you
What people love
- High 23% vitamin C concentration delivers strong brightening effects
- Absorbs quickly, leaving a silky, moisturized finish
- Cost-effective compared to Western vitamin C serums
Watch out for
- Irritates sensitive or dry skin causing redness and dermatitis-like rash
- Requires refrigeration and must be used quickly to avoid oxidation
- Runny texture leads to usage waste and sometimes sticky feel
Product details
Use caution
Skin Type
Product Traits
Key Ingredients
Where to buy
Real Reddit threads — 58 mentions across 25 threads
COSRX The Vitamin C 23 Serum on Reddit, in one place — 25 threads from r/koreanskincare, r/AsianBeauty and 3 more, summarized.
“COSRX Vitamin C 23”
Mentioned
“I forgot what some of the products I've tried but here are some of what I can remember.”
Mentioned
“I've also tried other brands from other countries.”
Mentioned
“Cosrx vitamin c is the only product that my skin had a bad reaction to 😩”
Cautionary
“the vitamin c gave me a dermatitis-like rash.”
Cautionary
“it has 23% pure vitamin c / L-ascorbic acid”
Cautionary
“Currently popular in my circle: vt reedle shot and pdrn, innisfree retinol, round lab sunscreen, aestura, numbuzin, torriden, cosrx vitamin c 23, mediheal masks, iope retinol, d'alba sunscreen, cell fusion c sunscreen”
Mentioned
“People here don’t touch the following brands much:”
Mentioned
“Why is CosRx not popular?”
Mentioned
“Their new vit-c serum blew up last year”
Mentioned
“all due to the fact they used old IOPE formula”
Mentioned
“I’m hoping here AP will release some of their old premium formulas under Cosrx”
Mentioned
“The vitamin c serum by cosrx. Does an amazing job with brightening!”
Positive
“Oh wow so many great products to choose from but I definitely would grab a bunch of Cosrx”
Positive
“I just bought the Cosrx vit c 13 and I like it so far.”
Positive
“Cosrx vitamin c 23.”
Positive
“I used it twice a day for about 4 months and I saw results in the first week.”
Positive
“Agree with CosRx Vit C... it did brighten my skin well.”
Positive
Dupes & Alternatives
Anua
Azelaic Acid Hyaluron Redness Soothing Serum
Better for Hyperpigmentation
6 shared traits
621 mentions