COSRX Advanced Pure Vitamin C 23% Serum — 0.7oz, Brightening Antioxidant with Vitamin E & Glutathione

COSRX Advanced Pure Vitamin C 23% Serum is a potent, lightweight vitamin C booster formulated to brighten dull skin, help reduce the look of fine lines, and even out skin tone.

This concentrated serum combines 23% pure ascorbic acid with supportive antioxidants — tocotrienol (a form of vitamin E) and glutathione — to deliver daytime radiance and antioxidant protection in a non-greasy texture. The formula has been updated to remove its distinctive scent while retaining the same active vitamin C strength, making it better suited for everyday use. Keep refrigerated after opening to slow oxidation and extend shelf life.

How quickly will I notice brighter, more even skin?

Results depend on skin type and consistency, but many users observe subtle brightening within 2–4 weeks and more visible evening of tone after continuous use for 6–12 weeks. Because the serum contains high-concentration ascorbic acid, it works by supporting skin’s surface renewal and protecting against free-radical damage.

• Immediate: lightweight radiance and smoother-looking surface after application.
• 2–4 weeks: gradual reduction in dullness and improved glow.
• 6–12 weeks: clearer reduction in uneven tone and the appearance of pigmented spots with regular use.

Is this vitamin C serum suitable for sensitive or acne-prone skin?

The serum is potent due to its 23% ascorbic acid content, so sensitivity is possible. COSRX recommends a patch test before full-face use and gradual introduction into your routine. If you have reactive skin, consider starting every other day or mixing a drop with your moisturizer.

• Patch test: apply to inner forearm and wait 24 hours for irritation check.
• Introduce slowly: begin with 1–2 times per week, increasing as tolerated.
• Layering tips: pair under sunscreen in the morning; avoid combining with strong acids or retinoids immediately.

How should I use and store the serum for best performance?

Shake the bottle gently 1–2 times before dispensing 2–3 drops and apply to clean, dry skin once or twice daily. For daytime use, always follow with a broad-spectrum SPF 30 or higher. To reduce oxidation and keep the formula effective longer, store the serum in the refrigerator after opening.

• Dosage: 2–3 drops per application, covering face and neck.
• Frequency: once or twice daily depending on tolerance and routine.
• Storage: refrigerate after opening; close cap tightly to limit air exposure.

What active ingredients are included and what do they do?

This serum pairs high-concentration pure vitamin C (ascorbic acid) with tocotrienol (a form of vitamin E) and glutathione to create an antioxidant-rich blend that supports skin radiance and helps counter environmental stressors. The combination is designed to complement vitamin C’s brightening properties with additional antioxidant resilience and support for an even-looking complexion.

• 23% pure ascorbic acid: primary brightening and antioxidant action.
• Tocotrienol (super vitamin E): supports skin barrier and antioxidant synergy.
• Glutathione: helps reduce the appearance of dullness and uneven pigmentation.

Who is this for: COSRX Advanced Pure Vitamin C 23% Serum is aimed at anyone seeking a high-strength vitamin C treatment to help brighten dull skin, refine the look of early fine lines, and even skin tone. It suits those comfortable using potent active ingredients and willing to introduce the product gradually; people with very reactive skin should take extra caution and consult a dermatologist if unsure.