COSRX Advanced Pure Vitamin C 23% Serum
A high-strength 23% pure vitamin C serum aimed at brightness and stubborn dark spots.
What it is
A concentrated serum with 23% pure L-ascorbic acid (the most studied, most active form of vitamin C) plus vitamin E and hyaluronic acid to support it. The texture is a slightly thick, fast-oxidising liquid that can tingle on application. It targets dullness, uneven tone and dark spots, and is aimed at skin already comfortable with actives.
What reviewers say
Long-term users report brighter skin and genuinely faded dark marks, and rate it as strong value for a high-percentage vitamin C. The recurring warnings are real: the initial sting or warmth, a short shelf life once opened as the formula darkens, and that sensitive or new-to-actives skin can find 23% too harsh. Storing it cool and using it up quickly are common tips.
What reviewers love
- High 23% pure vitamin C for real brightening power
- Can visibly fade dark spots with consistent use
- Vitamin E and hyaluronic acid help cushion the formula
- Strong value versus other high-strength vitamin C serums
Watch-outs
- Can sting or feel warm, especially at first
- Oxidises fairly fast, use within a few months
- Too strong for sensitive or beginner skin
Who it's for
| Resilient / experienced | Handles a high-percentage active for brightening |
| Dull / dark spots | Targets tone and marks with regular use |
| Sensitive | Approach with caution or start with a lower strength |
Key ingredients
- Pure vitamin C 23%: High-strength L-ascorbic acid for brightness and spots
- Vitamin E: Antioxidant that supports and stabilises vitamin C
- Hyaluronic acid: Adds hydration to offset any dryness
How to use it
Start slowly, a few mornings a week, on dry skin before moisturiser, then build up as tolerated. Always follow with sunscreen. Store it somewhere cool and dark, and replace it once it turns deep yellow or brown.
FAQ
Is 23% too strong for beginners?
It can be. If you are new to vitamin C, start once or twice a week or begin with a lower percentage and work up.
Why is it changing colour?
Pure vitamin C oxidises with light and air. A little darkening is normal, but deep brown means it is past its best.
Morning or night?
Most people use it in the morning for daytime antioxidant benefit, always under sunscreen.
The bottom line
A powerful, high-value vitamin C for skin that can handle strength and wants real brightening. Respect the sting, store it well, and use it up while it is fresh.
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