COSRX The Niacinamide 15 Serum in Beauty: NA. COSRX The Niacinamide 15 Serum in Beauty: NA. Highly concentrated serum that combines the maximum concentration of niacinamide with optimal ratios of synergistic ingredients for total acne control.. Suitable for all skin types Targets blackheads, whiteheads, pigmentation, and complexion. Cruelty-free. 20ml / .67 fl oz. After cleansing, during the serum phase, apply a few drops to the skin.. Use fingertips to gently massage and absorb the serum, starting from the center of the face working towards the edges.. CORX-WU75. COS317. COSRX - pronounced kos-are-ex - 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.