{"product_id":"cosrx-the-vitamin-c-13-serum-20ml-mirai-skin-cosrx-the-vitamin-c-13-serum-20ml","title":"COSRX The Vitamin C 13 Serum 20ml","description":"\u003ch2\u003eCOSRX The Vitamin C 13 Serum: An Entry-Level L-Ascorbic Acid for Brightening Beginners\u003c\/h2\u003e\n\u003cp\u003eCOSRX's Vitamin C 13 Serum sits at the gentler end of the pure L-ascorbic acid category. At 13% L-ascorbic acid, this is a true vitamin C serum, not the more stable ascorbyl derivatives that many K-beauty brands hide behind. It's formulated specifically for users who want measurable brightening and antioxidant protection but aren't ready to tolerate a 20% Skinceuticals CE Ferulic experience. The 20ml size reflects how this product should be used: fresh, finished within 3 months of opening, before oxidation turns it orange.\u003c\/p\u003e\n\u003cp\u003eCOSRX was founded in 2014 and built its reputation on minimalist routines that respect the skin barrier. This serum follows that philosophy. Beyond the vitamin C itself, the formula contains hyaluronic acid for buffering, vitamin E for antioxidant stability, and glycerin for barrier comfort. What it doesn't contain: ferulic acid, aggressive pH adjustments, or filler essences. The result is a vitamin C that the majority of Korean skincare users can tolerate daily without the stinging that 15 to 20% pure ascorbic acid typically produces.\u003c\/p\u003e\n\u003ch3\u003eWhat It Does\u003c\/h3\u003e\n\u003cp\u003eL-ascorbic acid at 13% inhibits tyrosinase (the enzyme that produces melanin), neutralizes free radical damage from UV exposure, and supports collagen synthesis in the dermis. Visible brightening shows over 4 to 8 weeks of daily morning use. It also thickens the collagen matrix gradually, giving longer-term firmness benefits that compound over months. This is textbook vitamin C skincare, formulated at a concentration that most barriers tolerate.\u003c\/p\u003e\n\u003ch3\u003eWho It's For\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eVitamin C beginners:\u003c\/strong\u003e The 13% concentration is a safer entry point than 20% formulas.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSun damage and hyperpigmentation:\u003c\/strong\u003e Daily AM use fades diffuse sun spots over 8 to 12 weeks.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDull or uneven skin tone:\u003c\/strong\u003e Brightens overall complexion and adds a natural glow.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSensitive skin that can't tolerate higher L-ascorbic:\u003c\/strong\u003e Gentler pH, fewer stinging reports.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBudget-focused routines:\u003c\/strong\u003e At $20.80 for 20ml, one of the most accessible pure vitamin C serums.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eKey Specs\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eVolume: 20ml\u003c\/li\u003e\n\u003cli\u003ePrice: $20.80\u003c\/li\u003e\n\u003cli\u003eHero actives: 13% L-ascorbic acid, hyaluronic acid, vitamin E\u003c\/li\u003e\n\u003cli\u003eTexture: lightweight, slightly watery serum\u003c\/li\u003e\n\u003cli\u003eFragrance: none\u003c\/li\u003e\n\u003cli\u003eShelf life once opened: 3 months before oxidation\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eHow to Use\u003c\/h3\u003e\n\u003cp\u003eApply 3 to 4 drops to clean, dry skin every morning after toner and before moisturizer. Let absorb for 60 to 90 seconds before layering. Always follow with SPF 30 or higher, because vitamin C increases photosensitivity as much as it protects against UV damage. Store the bottle in a cool, dark place with the cap tight. If the serum turns dark orange or brown, it has oxidized and should be replaced.\u003c\/p\u003e\n\u003cp\u003eBeginners should patch test first, then use every other morning for two weeks before moving to daily use. Tingling for 30 seconds is normal; persistent burning is not.\u003c\/p\u003e\n\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003ch4\u003eIs 13% enough to actually do anything?\u003c\/h4\u003e\n\u003cp\u003eYes. Clinical studies show L-ascorbic acid concentrations between 10% and 20% all produce brightening and antioxidant benefits, with diminishing returns above 15%. At 13%, you get most of the benefit with significantly less irritation risk than 20% formulas. For stubborn melasma or deep hyperpigmentation, you may want a higher concentration after your skin builds tolerance.\u003c\/p\u003e\n\u003ch4\u003eHow does this compare to Skinceuticals CE Ferulic?\u003c\/h4\u003e\n\u003cp\u003eDifferent leagues, different price points. CE Ferulic is 15% L-ascorbic plus 1% vitamin E and 0.5% ferulic acid, at a pH of 2.5 to 3.5, priced around $180. COSRX Vitamin C 13 is pure vitamin C at $20.80, no ferulic, gentler pH. For professionals who want the maximum antioxidant stack, CE Ferulic is still the benchmark. For everyday brightening at an accessible price, COSRX delivers 70% of the effect for 12% of the cost.\u003c\/p\u003e\n\u003ch4\u003eWhen should I see brightening results?\u003c\/h4\u003e\n\u003cp\u003eOverall radiance and glow: 2 to 3 weeks. Fading of diffuse sun damage: 6 to 8 weeks. Stubborn dark spots: 12 weeks of consistent daily use. Vitamin C works on skin cell turnover cycles, so patience matters. Combine with SPF for compounding benefits.\u003c\/p\u003e\n\u003ch4\u003eCan I use this with niacinamide?\u003c\/h4\u003e\n\u003cp\u003eYes, despite the old myth that the two neutralize each other. Modern formulations handle both fine, and clinical studies show they can be layered without canceling out. If you want to be cautious, use vitamin C in the morning and niacinamide at night. Otherwise, layer vitamin C first and niacinamide second.\u003c\/p\u003e\n\u003ch4\u003eWhat if my skin stings when I apply it?\u003c\/h4\u003e\n\u003cp\u003eLight tingling is normal for the first minute and fades as skin adapts. If stinging lasts longer than 2 minutes or feels like burning, dilute by mixing one drop of serum into a pea-sized amount of moisturizer for the first 2 weeks. Once tolerance builds, return to direct application.\u003c\/p\u003e\n\u003ch3\u003eRelated Products\u003c\/h3\u003e\n\u003cp\u003ePair with COSRX Advanced Snail 96 Mucin Power Essence as a calming buffer layer, or with niacinamide serums for stacked brightening. Always follow vitamin C with an SPF 50 from the Korean sunscreen collection.\u003c\/p\u003e\n\u003cp\u003eBrowse the full COSRX collection or related categories: Korean vitamin C serums, Korean brightening products.\u003c\/p\u003e\n","brand":"mirai-skin","offers":[{"title":"Default Title","offer_id":51741071507744,"sku":"51816163017076","price":10.4,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1004\/8333\/4432\/files\/76ac2966d58273becbba53f396f396f3.webp?v=1779694367","url":"https:\/\/usmirai-skin.com\/products\/cosrx-the-vitamin-c-13-serum-20ml-mirai-skin-cosrx-the-vitamin-c-13-serum-20ml","provider":"usmirai-skin.com","version":"1.0","type":"link"}