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[ DemythSkin Verdict ]

COSRX

COSRX The Vitamin C 23 Serum

Name: COSRX The Vitamin C 23 Serum
Brand: COSRX

SerumBrightening

Efficacy

Exceptional

4.5 / 5.0

Safety

Mostly Safe

4.0 / 5.0

System Verdict

This is a potent, high-impact vitamin C serum with serious brightening potential but equally serious irritation and stability risks. A true 23% ascorbic acid in a water-based system gives strong evidence-backed brightening and antioxidant effects if the pH is kept low enough, but the presence of denatured alcohol and multiple silicones, plus the need for very acidic pH for this concentration, means this will be too aggressive for many skin types and highly dependent on storage and tolerance rather than being a universally safe, elegant formula.

Active Ingredients Detected

S Tier: Gold StandardsHigh Clinical Proof | Skin-Transformative

Ascorbic Acid

A Tier: Good BasicsProven Results

PanthenolSqualaneSodium HyaluronateAdenosineAcetyl GlucosamineAllantoinTocopherolololNiacinamideHelianthus Annuus (Sunflower) Seed OilCarthamus Tinctorius (Safflower) Seed OilCamellia Japonica Seed Oil

B Tier: Supporting IngredientsPromising Ingredients

Ethyl Ascorbyl EtherCaffeineSodium ChlorideDextrinTocotrienolsElaeis Guineensis (Palm) OilBeta-Carotene

C Tier: Marketing IdolsHype | Limited or Weak Data

GlutathioneGardenia Florida Fruit ExtractGlycyrrhiza Glabra (Licorice) Root ExtractDaucus Carota Sativa (Carrot) Root Extract

D Tier: Potential IrritantsBe Cautious

Alcohol Denat.

What Each Ingredient Does

Water: solvent base
Ascorbic Acid: primary vitamin C active
Propanediol: solvent and penetration enhancer
Dimethicone: silicone emollient and texture enhancer
Tromethamine: pH adjuster and buffering agent
Panthenol: humectant and soothing agent
Ethyl Ascorbyl Ether: stable vitamin C derivative
Squalane: lightweight emollient and barrier support
Caffeine: antioxidant and circulation-support ingredient
Sodium Chloride: viscosity and stability adjuster
Sodium Hyaluronate: humectant for hydration
Sodium Sulfite: antioxidant preservative for stability
Disodium EDTA: chelating agent improving stability
Glutathione: antioxidant marketing addition
Adenosine: skin-conditioning and anti-wrinkle agent
Acetyl Glucosamine: skin-conditioning and hydration support
Gardenia Florida Fruit Extract: botanical antioxidant and colorant
Allantoin: soothing and skin-protective agent
Dextrin: stabilizer and texture modifier
Tocotrienols: vitamin E family antioxidant
Tocopherololol: vitamin E-like antioxidant
Elaeis Guineensis (Palm) Oil: emollient oil base
Butylene Glycol: humectant and solvent
Arginine: amino acid pH adjuster and conditioning

Full Ingredient List (INCI)

Water, Ascorbic Acid (23%), Propanediol, Dimethicone, Tromethamine, Panthenol, Ethyl Ascorbyl Ether, Squalane, Caffeine, Sodium Chloride, Sodium Hyaluronate, Sodium Sulfite, Disodium EDTA, Glutathione, Adenosine, Acetyl Glucosamine, Gardenia Florida Fruit Extract, Allantoin, Dextrin, Tocotrienols, Tocopherololol, Elaeis Guineensis (Palm) Oil, Butylene Glycol, Arginine, Niacinamide, Pentylene Glycol, Alcohol Denat., Helianthus Annuus (Sunflower) Seed Oil, Glycyrrhiza Glabra (Licorice) Root Extract, Methyl Trimethicone, Carthamus Tinctorius (Safflower) Seed Oil, Camellia Japonica Seed Oil, Daucus Carota Sativa (Carrot) Root Extract, Beta-Carotene From the brand Previous page COSRX Sommer-Highlights COSRX Sommer-Essentials Next page Product Description Previous page Next page 1 Results 2 Benefits 3

Frequently Asked

Is COSRX The Vitamin C 23 Serum worth it?

COSRX The Vitamin C 23 Serum scores 4.5 out of 5.0 for efficacy (Exceptional) and 4.0 out of 5.0 for safety (Mostly Safe) on DemythSkin's independent ingredient analysis. This is a potent, high-impact vitamin C serum with serious brightening potential but equally serious irritation and stability risks. A true 23% ascorbic acid in a water-based system gives strong evidence-backed brighteni

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

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

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

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

How is COSRX 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: 2026-08-25. 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.