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[ DemythSkin Verdict ]

COSRX Advanced The Vitamin C 23 Serum

SerumBrightening

Efficacy

Exceptional

4.6 / 5.0

Safety

Mostly Safe

4.2 / 5.0

System Verdict

This is a clinically serious brightening/antioxidant serum with an aggressive but well-supported vitamin C system that will work beautifully on resilient skin and absolutely terrorize an unprepared barrier. Efficacy is high because you get both pure ascorbic acid and S Tier 3‑O‑ethyl ascorbic acid, reinforced by niacinamide, licorice, glutathione, tocotrienol and multiple antioxidants, but the very high acid load and potential low pH mean that users with sensitive or compromised skin will trade results for stinging, dryness and barrier stress unless they buffer with a robust moisturizer and introduce it slowly.

Active Ingredients Detected

S Tier: Gold StandardsHigh Clinical Proof | Skin-Transformative

Ascorbic Acid

A Tier: Good BasicsProven Results

3-O-Ethyl Ascorbic AcidAcetyl GlucosamineAdenosineAllantoinAqua / WaterArginineCarthamus Tinctorius (Safflower) Seed OilDimethiconeHelianthus Annuus (Sunflower) Seed OilHydrogenated LecithinNiacinamidePanthenolSqualaneSodium HyaluronateTocopherol

B Tier: Supporting IngredientsPromising Ingredients

Beta-CaroteneButylene GlycolCaffeineDisodium EDTAElaeis Guineensis (Palm) OilMethyl Glucose SesquistearateMethyl TrimethiconePolyglyceryl-3 Methylglucose DistearatePotassium Cetyl PhosphatePropanediolSodium ChlorideSodium SulfiteTocotrienolCarbomerCentella Asiatica ExtractTromethamine

C Tier: Marketing IdolsHype | Limited or Weak Data

Glycyrrhiza Glabra (Licorice) Root ExtractDaucus Carota Sativa (Carrot) Root ExtractGlutathione

D Tier: Potential IrritantsBe Cautious

Ethylhexylglycerin

What Each Ingredient Does

3-O-Ethyl Ascorbic Acid: Stable vitamin C brightening antioxidant
Acetyl Glucosamine: Supports exfoliation and brightening
Adenosine: Anti-aging, improves wrinkles
Allantoin: Soothing, reduces irritation
Aqua / Water: Solvent base for the formula
Arginine: pH adjuster and skin-conditioning
Ascorbic Acid: Pure vitamin C antioxidant, brightening
Beta-Carotene: Pro-vitamin A antioxidant pigment
Butylene Glycol: Humectant and solvent
Caffeine: Antioxidant, may reduce puffiness
Carthamus Tinctorius (Safflower) Seed Oil: Emollient, linoleic-rich plant oil
Dimethicone: Silicone emollient, slip and barrier support
Disodium EDTA: Chelating agent, stabilizes formula
Elaeis Guineensis (Palm) Oil: Emollient, occlusive plant oil
Ethylhexylglycerin: Preservative booster, humectant
Glycyrrhiza Glabra (Licorice) Root Extract: Brightening, anti-inflammatory
Helianthus Annuus (Sunflower) Seed Oil: Emollient, barrier support
Hydrogenated Lecithin: Emulsifier, helps delivery of actives
Methyl Glucose Sesquistearate: Emulsifier and texture enhancer
Methyl Trimethicone: Volatile silicone for light texture
Niacinamide: Multifunction brightening and barrier support
Panthenol: Humectant and soothing provitamin B5
Polyglyceryl-3 Methylglucose Distearate: Emulsifier, helps stabilize emulsion
Potassium Cetyl Phosphate: Anionic emulsifier, stabilizes oil phase

Full Ingredient List (INCI)

3-O-Ethyl Ascorbic Acid Acetyl Glucosamine Adenosine Allantoin Aqua/water Arginine Ascorbic Acid BETA-CAROTENE Butylene Glycol Caffeine Carthamus Tinctorius (Safflower) Seed Oil Dimethicone Disodium EDTA Elaeis Guineensis (Palm) Oil Ethylhexylglycerin Glycyrrhiza Glabra (Licorice) Root Extract Helianthus Annuus (Sunflower) Seed Oil Hydrogenated Lecithin Methyl Glucose Sesquistearate Methyl Trimethicone Niacinamide Panthenol Polyglyceryl-3 Methylglucose Distearate Potassium Cetyl Phosphate Propanediol Squalane Sodium Chloride Sodium Hyaluronate Sodium Sulfite Tocopherol Tocotrienol Carbomer Centella Asiatica Extract Daucus Carota Sativa (Carrot) Root Extract Glutathione Tromethamine

Frequently Asked

Is COSRX Advanced The Vitamin C 23 Serum worth it?

COSRX Advanced The Vitamin C 23 Serum scores 4.6 out of 5.0 for efficacy (Exceptional) and 4.2 out of 5.0 for safety (Mostly Safe) on DemythSkin's independent ingredient analysis. This is a clinically serious brightening/antioxidant serum with an aggressive but well-supported vitamin C system that will work beautifully on resilient skin and absolutely terrorize an unprepared barrier. Efficacy is h

What are the key active ingredients in COSRX Advanced The Vitamin C 23 Serum?

COSRX Advanced The Vitamin C 23 Serum contains these gold-standard actives with strong clinical evidence: Ascorbic Acid.

Does COSRX Advanced The Vitamin C 23 Serum contain fragrance or known irritants?

DemythSkin flags these ingredients in COSRX Advanced The Vitamin C 23 Serum as potential irritants: Ethylhexylglycerin.

How is COSRX Advanced The Vitamin C 23 Serum scored?

DemythSkin grades every product on two independent axes: efficacy (whether the ingredients have clinical evidence of working) and safety (irritation and sensitisation risk). Ingredients are classified S through D against a database of over 3,000 compounds. No brand pays for a score.

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Analysis last updated: 2026-07-12. DemythSkin is an independent ingredient analyzer. Scores are computed by a deterministic rubric from published clinical evidence — no brand pays for a score. DemythSkin earns commission from affiliate links (Amazon Associates and others). Scores are computed before any commercial relationship — the link follows the verdict, never the other way around.