COSRX The Niacinamide 15 Serum

COSRX The Niacinamide 15 Serum

Target excess oil, visible pores, post-breakout marks, and uneven texture with the COSRX The Niacinamide 15 Serum, a high-strength daily serum designed to help refine and balance blemish-prone skin while leaving it smoother, clearer, and more even-looking.

Formulated with 15% niacinamide, zinc PCA, N-acetylglucosamine, and allantoin, this lightweight serum helps support total breakout care and oil control. Niacinamide helps reduce the look of excess shine, enlarged pores, and uneven tone, while zinc PCA helps support sebum balance for a fresher, less greasy-looking complexion. N-acetylglucosamine helps improve the appearance of post-acne marks and rough texture, while allantoin helps comfort and soothe the skin.

The COSRX The Niacinamide 15 Serum is a great choice for anyone looking for a K-beauty niacinamide serum, oil-control serum, or a pore-refining Korean skincare serum for acne-prone skin. Its fast-absorbing, non-heavy texture makes it easy to layer into both morning and evening routines for skin that looks clearer, smoother, and more balanced over time.

Size: 20ml / 0.67 fl. oz

Overview

The COSRX The Niacinamide 15 Serum is a concentrated treatment serum created to help support oil control, pore care, texture refinement, and post-breakout care in one step. Designed especially for oily, combination, and blemish-prone skin, it helps improve the look of shine, congestion, and uneven skin tone while keeping skin feeling comfortable.

Study results

According to the brand's reported clinical results after 4 weeks of use, this serum showed:

• 50% decrease in whiteheads
• 48.07% improvement in oiliness
• 45.27% reduction in visible pores
• 42.27% decrease in blackheads
• 24% reduction in redness
• 19.47% improvement in pigmentation

The brand also states that the formula is non-comedogenic tested, dermatologist tested, and hypoallergenic tested. Individual results may vary.

Key benefits

• Helps reduce the look of excess oil and shine
• Supports improvement in visible pores and rough texture
• Helps improve the appearance of post-acne marks and uneven tone
• Formulated with 15% niacinamide, zinc PCA, N-acetylglucosamine, and allantoin
• Fast-absorbing texture with a comfortable finish
• Great for oily, combination, and blemish-prone skin

How to use

Shake 1–2 times before use. After cleansing and toning, apply 2–3 drops to problem areas or the entire face. Gently pat until absorbed, then follow with moisturizer. Use sunscreen during the daytime. Patch testing is recommended before full facial use.

Why we love it

Niacinamide is one of the most researched and versatile actives in Korean skincare — and 15% is as high as it goes without entering irritation territory for most skin types. The COSRX The Niacinamide 15 Serum is built around that maximum-efficacy concentration, and then supported by three synergistic actives chosen specifically to address the full scope of oily and blemish-prone skin concerns: zinc PCA to regulate sebum and prevent breakouts before they start, N-acetylglucosamine (NAG) to fade post-acne marks and gently exfoliate, and allantoin to keep everything calm while the actives do their work. What makes this particularly impressive is the clinical backing: 50% decrease in whiteheads and 45.27% reduction in visible pores in just 4 weeks. The formula contains only 14 ingredients — no fillers, no fragrance, no botanical padding — which is pure COSRX philosophy applied at its most concentrated. At BestSkincareUSA.com, it's our top single-serum recommendation for anyone whose primary skin concerns are oil, pores, and post-blemish marks.

Key ingredients deeper dive

• 15% niacinamide — maximum-efficacy oil and pore control — The clinical ceiling for niacinamide efficacy without broad irritation risk. At 15%, niacinamide actively regulates sebum production, visibly minimizes enlarged pores, improves uneven skin tone, fades the look of dark spots and post-acne marks, and strengthens the skin barrier — making it one of the most comprehensive actives in a single ingredient across all Korean skincare brands.
• Zinc PCA for sebum regulation and breakout prevention — Combines zinc's sebum-controlling and antibacterial properties with PCA's hydrating effect — reducing oiliness and preventing the environmental conditions that allow blemish-causing bacteria to thrive, without the dryness that harsher acne-fighting ingredients cause.
• N-acetylglucosamine (NAG) for gentle exfoliation and pigmentation improvement — A mild exfoliant and melanin-inhibitor that helps fade post-acne marks, smooth rough texture, and support cellular renewal — working at the surface to visibly clarify the complexion over time while complementing niacinamide's deeper pigmentation work.
• Allantoin for soothing and barrier comfort — Keeps the skin calm and comfortable while the 15% niacinamide and zinc PCA do their concentrated work — essential in a formula at this activity level to prevent sensitization and maintain the barrier integrity that oily and blemish-prone skin often lacks.
• Tocopherol (Vitamin E) for antioxidant protection — Rounds out the formula with free-radical defense, supporting the skin's resilience against environmental damage that can worsen the look of uneven tone and post-blemish marks.
• Only 14 ingredients — fragrance-free, fungal-acne safe, reef-safe — A no-filler, no-fragrance formula with every ingredient serving a defined function. Non-comedogenic tested, dermatologist tested, and hypoallergenic tested — one of the cleanest high-strength niacinamide serums available in COSRX's lineup.

Who it's for

The COSRX The Niacinamide 15 Serum is designed for oily, combination, and blemish-prone skin that wants a single concentrated serum addressing oil control, visible pores, post-acne marks, and uneven tone simultaneously. It's particularly effective for anyone who has used lower-concentration niacinamide products without seeing the results they wanted, and for those building a results-focused Korean face routine around acne and pore care. Because it's hypoallergenic tested and fragrance-free, sensitive skin types dealing with oiliness and blemishes can also use it — patch testing first is recommended at this concentration.

Pro tips and pairings

Shake the bottle 1–2 times before each use to ensure the formula is evenly mixed. Apply the COSRX The Niacinamide 15 Serum after the COSRX AHA/BHA Clarifying Treatment Toner in the evening — the toner's exfoliating acids prepare the skin to absorb the niacinamide more effectively. Follow with the COSRX Advanced Snail 96 Mucin Power Essence to layer hydration and barrier repair over the active treatment — snail mucin's film-forming properties also help lock the niacinamide in contact with the skin. Always finish your morning routine with a broad-spectrum SPF when using this serum, as niacinamide's pigmentation work is significantly more effective when the skin is protected from UV exposure that would otherwise continue forming new dark spots.

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