COSRX Advanced The Vitamin C 23 Serum 20g 23% Pure Vitamin C Dark Spot Korean

COSRX Advanced The Vitamin C 23 Serum 20g 23% Pure Vitamin C Dark Spot Korean

COSRX Advanced The Vitamin C 23 Serum — 23% Pure Vitamin C, 20 g / 0.7 oz
With Super Vitamin E (Tocotrienol) + Glutathione + Hyaluronic Acid | High-Strength Korean Brightening Serum

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COSRX Advanced The Vitamin C 23 Serum is a high-strength brightening serum built on 23% pure Vitamin C (L-Ascorbic Acid) — the most researched and most potent form of vitamin C in skincare. It targets dull, uneven skin tone, the look of dark spots and post-acne marks, and early signs of aging.

What sets this formula apart is the antioxidant network supporting it: Super Vitamin E (Tocotrienol) — which has substantially higher antioxidant activity than standard tocopherol — plus Glutathione, a master antioxidant. Together they help stabilize pure vitamin C, which is notoriously unstable on its own, so it delivers more comfortably and effectively to the skin.

The serum uses a distinctive double-layered formula with an oil layer resting on top of the vitamin C layer, which helps slow oxidation and leaves a moisturizing finish. Just shake gently before each use to combine the layers.

Important: this is a high-concentration formula intended for people who already have experience using vitamin C serums. If you're new to actives, COSRX's 13% version is the gentler starting point.

Why customers love it:

• 23% pure Vitamin C (L-Ascorbic Acid) — high-strength, the gold-standard form
• Super Vitamin E (Tocotrienol) — significantly higher antioxidant activity than standard vitamin E
• Glutathione — master antioxidant, supports clarity and brightening
• Hyaluronic Acid + Panthenol + Squalane — hydration so the potency doesn't come at the cost of comfort
• Allantoin + Licorice Root Extract — soothing support
• Helps fade the look of dark spots, acne marks, and uneven tone
• Antioxidant protection against daily environmental stress
• Supports the look of firmness, texture, and radiance
• Double-layered oil-on-serum formula to help slow oxidation
• No artificial fragrance
• Dermatologist-tested — found to be non-irritating in a Primary Dermal Irritation Study (30 subjects, 24 hours)
• Made in South Korea, cruelty-free

Key Ingredients:

• Ascorbic Acid (23%) — pure vitamin C, the most-studied brightening and antioxidant active
• Tocotrienols (Super Vitamin E) — high-potency antioxidant that supports vitamin C's stability and effectiveness
• Glutathione — master antioxidant for clarity and even tone
• Sodium Hyaluronate — hydration
• Adenosine — supports elasticity and the look of fine lines
• Niacinamide, Panthenol, Allantoin, Licorice Root Extract — tone support and soothing
• Squalane, Camellia & Safflower Seed Oils — the nourishing oil layer

A few honest notes on what to expect:

• The scent: pure ascorbic acid naturally has a faint coppery or metallic smell. Because this serum contains no artificial fragrance to mask it, you may notice it. This is completely normal for high-concentration L-ascorbic acid serums.
• The two layers: you'll see an oil layer sitting on top. That's intentional — it helps slow oxidation. Shake gently 1–2 times before applying to combine.
• Storage: vitamin C oxidizes over time with exposure to light, heat, and air. Store in a cool, dark place — many users keep it in the refrigerator to extend freshness.
• A tingle on application is common with a 23% formula, especially at first. Persistent stinging or burning is not — reduce frequency or discontinue if that happens.

Perfect for:

• Dark spots, post-acne marks, sun spots, and uneven skin tone
• Dullness and lack of radiance
• Early signs of aging — fine lines, loss of firmness
• Experienced vitamin C users ready to step up from 10–15% formulas
• Anyone wanting antioxidant protection layered under daily SPF
• COSRX fans building out a full routine

How to use:

1. Shake gently 1–2 times to combine the oil and serum layers.
2. After cleansing and toning, apply 2–3 drops to the entire face, avoiding the eye area.
3. Pat gently to help absorption.
4. Follow with moisturizer.
5. Always follow with broad-spectrum SPF 30+ during the day — this is not optional with vitamin C.
6. Beginner protocol: start every other day and build up as your skin adjusts.
7. Patch test on your inner arm before applying to the face — COSRX specifically recommends this given the concentration.

Layering guidance (important):
Because of the high 23% concentration, COSRX recommends not using this serum at the same time as copper peptide products or retinol/retinal products. Instead, use them at different times of day — for example, vitamin C in the morning and your peptide or retinol product in the evening. This lets each active absorb and work properly.

Product Details:

• Brand: COSRX
• Product: Advanced The Vitamin C 23 Serum
• Size: 20 g / 0.7 oz (dropper bottle)
• Form: Serum (double-layer: oil over serum)
• Key Ingredients: Ascorbic Acid 23%, Tocotrienols (Super Vitamin E), Glutathione, Sodium Hyaluronate, Adenosine, Niacinamide, Panthenol, Allantoin, Licorice Root Extract
• Skin Type: All — best suited to those experienced with vitamin C
• Features: Fragrance-Free, Dermatologist-Tested, Cruelty-Free, Korean Beauty (K-Beauty)
• Country of Origin: Made in South Korea

Shipping & Returns:
Ships within 1 business day, securely packaged to protect the glass dropper bottle. Returns accepted per the policy listed above. Send a message before buying if you have any questions and I'll respond quickly.