COSRX The Vitamin C 13 Serum – Brightening Serum with 13% Pure Ascorbic Acid
COSRX The Vitamin C 13 Serum is a lightweight, water-based facial serum designed to improve the appearance of dull, uneven-toned, and rougher-looking skin. Its concept is clear from the name: the number 13 refers to a 13% concentration of pure vitamin C in the form of ascorbic acid. It is intended for daily use by those who want to combine the benefits of vitamin C with hydrating comfort rather than opt for the more intensive 23% version in the same line.
Two Forms of Vitamin C and a Formula That Values Freshness
The foundation of this serum is pure ascorbic acid, complemented by 3-O-Ethyl Ascorbic Acid. This combination keeps the focus on brighter, more even-looking skin, but the formula is not built around a single active ingredient alone. It also contains moisture-supporting and skin-comforting ingredients, making it feel more like a thoughtfully formulated everyday serum than simply a concentrated vitamin C solution. One notable practical detail is that the manufacturer recommends storing the opened bottle in the refrigerator, as pure ascorbic acid is sensitive to environmental factors.
- 13% pure ascorbic acid: the formula’s key feature, intended to improve the appearance of dull skin and uneven tone and reduce the visibility of pigmentation spots.
- Tocotrienols to complement vitamin E: antioxidants from the vitamin E family that reinforce the formula’s antioxidant profile and give it a purpose beyond brightening alone.
- Hydrating support: panthenol, sodium hyaluronate, and allantoin help maintain a moisturized feel, so vitamin C is delivered here with added comfort for the skin.
At first, the serum is very fluid—almost watery—spreads easily, and absorbs quickly without leaving noticeable stickiness. It fits into the serum step of a routine after cleansing, making it a good choice when you want a lightweight texture that will not weigh down subsequent products. COSRX The Vitamin C 13 Serum stands out less for an elaborate list of promises than for its clear 13% pure vitamin C formula, which balances active performance with a hydrating base.
Usage
After cleansing and toning your skin, apply 2-3 drops of COSRX The Vitamin C 13 Serum to your fingertips and gently pat it onto your face, focusing on areas that require brightening or have dark spots. Allow the serum to absorb fully before applying your moisturizer and sunscreen. For best results, use the serum in the morning and gradually increase usage to daily as your skin adapts. Always perform a patch test before full application and store the product in a cool, dark place to maintain its efficacy.
Ingredients
Aqua, Ascorbic Acid (13%), Butylene Glycol, Dipropylene Glycol, Tromethamine, 3-O-Ethyl Ascorbic Acid, Panthenol, Acetyl Glucosamine, Caffeine, Sodium Hyaluronate, Sodium Sulfite, Disodium EDTA, Glutathione, Adenosine, Gardenia Florida Fruit Extract, Allantoin, Dextrin, Squalane, Tocotrienols, Tocopherol, Elaeis Guineensis (Palm) Oil, Arginine, Niacinamide, Pentylene Glycol, Glycyrrhiza Glabra (Licorice) Root Extract
The manufacturer is responsible for the product’s ingredients. Due to possible changes, we always recommend checking the ingredient list directly on the packaging.



In today's cosmetics market, where labels often resemble pages from a chemistry textbook, Cosrx Cosmetics stands out with its simple yet astonishingly effective approach. Their products contain only carefully selected active ingredients:
However, Cosrx Cosmetics cares not only for your skin but also for the planet. All their products are manufactured following the highest quality standards, without cruel animal testing. Additionally, the brand actively strives to reduce packaging waste and promotes sustainable production practices. Isn't it reassuring to know that your chosen cosmetics contribute to a cleaner planet? It's a double benefit—your skin glows, and the world becomes a little better.









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