COSRX AC Collection Blemish Spot Clearing Serum in Beauty: NA. COSRX AC Collection Blemish Spot Clearing Serum in Beauty: NA. Formulated with proprietary COSRX Centella AC-Rx Complex, the AC Collection Blemish Spot Clearing Serum not only treats acne, but also helps the skin recover without any irritation. This blemish-clearing serum can be used daily to clear acne and brighten skin. The triple blemish care system works to calm, brighten, and strengthen skin with CentellAC-Rx complex and 4% Niacinamide.. Madecassic acid calms and protects, Asiaticoside keeps skin clear, and Asiatic acid strengthens the skin barrier to maintain a balanced complexion. 4% Niacinamide brightens and evens skin tone. Ceramides strengthen the skin barrier and boost hydration. 1.35 fl oz. Apply an appropriate amount gently to sensitive skin; lightly pat into skin to absorb. CORX-WU52. COS262. COSRX is committed to making ingredient-oriented, high-performance skincare. Using a minimal number of highly effective natural extracts in concentrated doses, COSRX products deliver visible results by treating skin with only the essentials it needs and nothing it doesn't.