COSRX Advanced Pure Vitamin C 23% Serum
A high-strength vitamin C serum aimed at brightness and stubborn dark spots.
What it is
A concentrated serum with a high level of pure vitamin C, backed by vitamin E and glutathione to boost brightening, plus hyaluronic acid and a soothing ingredient to soften the hit. The texture is a slightly thick liquid in a dark bottle, and you attach the dropper only when you first open it, because pure vitamin C loses strength quickly once exposed to air and light. It targets dullness, uneven tone and dark spots, and is aimed at skin already used to strong actives. This is the 20ml size.
What reviewers say
Reviewers who stick with it report noticeably brighter, more even skin within a few weeks and slowly fading post-acne marks, and many rate it as strong value for such a high-strength vitamin C. The recurring warnings are real: it can tingle or feel warm at first (this usually settles after a few uses), it darkens and loses strength fairly fast once opened so it is best used up quickly, and sensitive or beginner skin can find it too harsh.
What reviewers love
- High-strength vitamin C for real brightening power
- Can visibly fade dark spots with steady use
- Vitamin E and glutathione add to the brightening
- Dark bottle and attach-later dropper help keep it fresh
Watch-outs
- Can tingle or feel warm, especially at first
- Loses strength fairly fast once opened, so use it up
- Too strong for sensitive or beginner skin
Who it's for
| Experienced / resilient | Handles a high-strength active for brightening |
| Dull / dark spots | Targets tone and marks with steady use |
| Sensitive / beginner | Approach with caution or start with a gentler vitamin C |
Key ingredients
- Vitamin C (high strength): Brightens and helps fade dark spots
- Vitamin E and glutathione: Support and boost the brightening effect
- Hyaluronic acid: Adds hydration to offset any dryness
How to use it
When you first open it, attach the dropper. Start slowly, a few mornings a week on dry skin before moisturiser, then build up as your skin gets used to it. Always follow with sunscreen, keep the bottle somewhere cool and dark, and replace it once it turns deep yellow or brown.
FAQ
Is it 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-strength serum and work up.
Why is it changing colour?
Pure vitamin C darkens as it reacts with air and light. A little 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, good-value vitamin C for skin that can handle strength and wants real brightening. Respect the tingle, store it well, and use it up while it is fresh.
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