COSRX Pure Vitamin C 13% Serum — 0.67 oz Brightening Vitamin C with Hyaluronic Acid & Vitamin E for Uneven Tone

COSRX Pure Vitamin C 13% Serum is a concentrated daily brightening serum that blends pure ascorbic acid with vitamin E, hyaluronic acid, and glutathione to help even tone and hydrate skin.

This lightweight Korean serum delivers an effective level of pure vitamin C (13% ascorbic acid) alongside supportive antioxidants and moisture-binding ingredients to address dullness, uneven pigmentation, and fine lines. The formula is designed for daily use; it absorbs quickly without leaving a sticky finish and layers well under moisturizers and sunscreen. Keep in mind vitamin C serums are oxidation-prone, so store it cool after opening and perform a patch test before full-face application.

How should I add this serum to my morning and evening routine?

Apply 2–3 drops to clean, dry skin once or twice daily depending on tolerance. In the morning, always follow with a broad-spectrum SPF 30+; at night pair it with a gentle moisturizer. Shake the bottle before use to ensure uniform texture and actives.

• Use on cleansed face and neck, avoiding direct contact with eyes.
• Press 2–3 drops into skin and let absorb before layering other products.
• Use sunscreen during daytime for protection and results.
• Refrigerate after opening to slow oxidation and maintain potency.

Will this serum suit sensitive or reactive skin?

The 13% ascorbic acid concentration is potent and can irritate sensitive skin, so start gradually. Perform a 24-hour patch test on the inner forearm or behind the ear; discontinue if you experience redness or persistent stinging. You can also reduce frequency to every other day until tolerance builds.

• Patch test before full-face use and wait 24 hours for a reaction check.
• Begin with small amounts and limit application to evenings if needed.
• Layer with soothing, fragrance-free moisturizers to minimize irritation.

What visible improvements can I expect and when?

Consistent use can help brighten dullness and make skin tone appear more uniform over several weeks. Hyaluronic acid supplies immediate moisture and plumps fine lines, while vitamin E and glutathione support antioxidant protection. Individual results vary with skin type and routine consistency.

• Immediate: increased hydration and smoother skin texture.
• 4–8 weeks: gradual reduction in dullness and more even tone.
• Long-term: enhanced radiance when paired with sun protection.

How should I store and preserve this vitamin C serum?

Ascorbic acid oxidizes when exposed to heat, light, and air, so keep the bottle tightly closed and stored in a cool, dark place. COSRX recommends refrigerating after opening to extend freshness. If the serum darkens or develops a sour smell, discard it and replace the product.

• Shake before each use to mix actives evenly.
• Refrigerate once opened to slow oxidation.
• Replace if color changes noticeably or scent turns off.

Who is this for? This serum is aimed at anyone seeking a stronger topical vitamin C treatment to target dullness, uneven skin tone, and early signs of aging while also delivering hydration. It suits those comfortable introducing a potent active into their routine and willing to follow storage and sun-protection guidance. If you have very sensitive or rosacea-prone skin, consult a dermatologist and proceed with patch testing before regular use.