The Vitamin C 23 Serum — Reddit Reviews
by COSRX
Updated August 4, 2026
23% pure L-ascorbic acid concentration offers potent brightening effects and rapid fading of dark spots
What the community says
High-potency 23% vitamin C serum with hyaluronic acid delivers strong brightening and fading of hyperpigmentation but can be harsh and irritating on sensitive, eczema-prone, or compromised skin.
What this means for you
What people love
- 23% pure L-ascorbic acid concentration offers potent brightening effects and rapid fading of dark spots
- Hyaluronic acid provides hydration to offset some dryness from vitamin C
- Cost-effective compared to pricier vitamin C serums from Western brands
Watch out for
- Formula can cause redness, irritation, or dermatitis-like reactions, especially for sensitive or eczema-prone skin
- Requires refrigeration to prevent oxidation and has a short 2-month shelf life after opening
- Sticky, slightly oily texture with a strong, unpleasant scent that many find off-putting
Product details
Concerns
Key Ingredients
Where to buy
Real Reddit threads
20 threads from r/koreanskincare, r/AsianBeauty +3 more
“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
“I love this cosrx vitamin c!!!”
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. I used it twice a day for about 4 months and I saw results in the first week.”
Positive
“Agree with CosRx Vit C.”
Positive
“it did brighten my skin well.”
Positive
Dupes & Alternatives
Anua
Azelaic Acid 10 Hyaluron Redness Soothing Serum
Better for Hyperpigmentation
5 shared traits
499 mentions
