COSRX Advanced The Vitamin C 23 Serum | Super Vitamin E + Hyaluronic Acid
Choose an option
- 23% L-Ascorbic
- Fast Results
- Dullness
- Advanced Users
Only 5 left in stock
The potent end of vitamin C.
Twenty-three percent L-ascorbic acid is not a gentle derivative and should not be treated as one. It works quickly on dullness and marks, and it stings. If you have never used vitamin C, start somewhere else and come back to this.
- 23% stated
- Not for beginners
- Night use
How it feels
A thick, slightly tacky serum. Warmth and tingling on application are expected at this concentration and settle over the first fortnight.
Key ingredients
L-Ascorbic Acid
At 23%, the pure and most-studied form of vitamin C. Potent and unstable - it works fast and degrades fast.
Vitamin E
Stabilises the ascorbic acid and works alongside it, a pairing with good evidence behind it.
About the product
COSRX's Pure Vitamin C 23 Serum sits at the potent end of the category, and it is worth being direct about who should buy it.
L-ascorbic acid at 23% is the pure, most-studied form of vitamin C - not a gentle derivative. It works quickly on dullness and uneven tone, and it stings. Warmth and tingling on application are expected at this concentration rather than a sign something is wrong, though they should settle over the first fortnight.
If you have never used vitamin C, this is not where to start. A derivative or a lower-strength serum builds tolerance first; jumping to 23% is how people conclude vitamin C does not suit them.
The second consideration is stability. L-ascorbic acid oxidises on contact with air and light, which is why this comes in a small 20ml bottle - it is meant to be finished before it degrades. Vitamin E stabilises it, a pairing with good evidence behind it. If the serum turns deep yellow or brown, it has oxidised and should be replaced.
Use at night, every third evening at first. Sunscreen the following morning is essential.
Why we stock it
We stock this alongside gentler vitamin C options deliberately, and we are direct with customers about which they should buy. At 23% L-ascorbic acid this is the potent end of the category and not a beginner product.
Product information
- Brand
- COSRX
- Skin concerns
- hydration, barrier, dullness, dark-spots, texture, brightening
Ingredients
23% L-Ascorbic Acid (Pure Vitamin C), Vitamin E, Glutathione, Allantoin
Care & Use
How to Use
In the morning, apply a thin layer to clean dry skin, wait a few minutes, then follow with moisturiser and sunscreen. Start every other day. Store away from light and heat.
- 1.
In the morning, apply
In the morning, apply a thin layer to clean dry skin, wait a few minutes, then follow with moisturiser and sunscreen.
- 2.
Start every other day
Start every other day.
- 3.
Store away from light
Store away from light and heat.
Product details
Product details
- Brand
- COSRX
- Product type
- Beauty
- SKU
- cosrx-pure-vitamin-c-23-serum-20ml-20-g
- Volume
- 20 g
Frequently asked questions
Is 23% too strong for me?
If you have not used vitamin C before, yes - start with a derivative or a 10-15% serum. This is for people who already tolerate vitamin C and want more potency.
Why does it sting?
L-ascorbic acid at 23% is highly acidic. Warmth and tingling are expected and usually settle over a fortnight. Persistent burning or redness means it is too strong for you.
It has turned yellow - is it still good?
A slight yellowing is normal with age. Deep yellow or brown means it has oxidised and lost potency - replace it. The small bottle size is deliberate for this reason.
Can I use it with retinol or acids?
Not on the same night. Alternate evenings at most, and only once your skin tolerates each on its own.
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