The Niacinamide 15 Serum
A pore-refining serum led by niacinamide; this bottle's own list does not declare a percentage, so the 15 in the name is not claimed here.
No reviews yet20ml
$9.50 per 10 ml
- Korean-market formula
- Ships from California or direct from Korea
- Korean barcode and batch code intact
- Suited to
- DryDehydratedSensitiveCompromised barrier
- Helps with
- DehydrationBarrier weaknessEarly environmental damageUneven tone and dullness
Sold out.
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- 30-day returns
- Free US shipping on orders of $100 or more
- Tracked delivery to your door
How it works
A niacinamide serum is bought for how the surface looks: tone, shine, and the size pores appear to be. This is the niacinamide step in COSRX's line, a short, thin formula that goes on after toner and before moisturizer. Skin that turns shiny by midday and reads uneven in tone is the case it fits, and it is a daily step rather than an occasional one. Niacinamide is one of the few actives that sits happily in both the morning and the evening routine. Twice a day, and it layers under anything else already in place.
How to use
- Use the Niacinamide 15 Serum after toner and before moisturizer, morning and evening.
- Three or four drops covers the face. Press it in rather than rubbing it across the skin.
- Toner first, this second, then moisturizer, and sunscreen last in the morning.
- Twice a day, every day. Do not layer it with a second niacinamide product; one step of it is enough in a routine.
COSRX The Niacinamide 15 Serum
What does The Niacinamide 15 Serum actually do for the skin?
Niacinamide sits third on the list, right behind water and pentylene glycol, with Zinc PCA and Acetyl Glucosamine following close behind. That order places niacinamide near the front of a short, pore-focused formula, with trehalose and allantoin further down to round out the hydrating, calming base. The combination targets pore appearance and tone rather than acting as a broad hydrating serum.
Is this serum suitable for oily, pore-prone skin?
The list has no fragrance, no essential oil, no added silicone, no paraben, and no mineral oil. That profile suits oily and pore-prone skin looking for a lightweight, fragrance-free niacinamide serum. This bottle's own list does not declare a percentage for niacinamide, so despite the name, no specific strength figure is claimed here.
How long before pores or tone look different with regular use?
Niacinamide and zinc PCA both work toward a clearer, more even look with sustained daily application rather than a single dose. Visible pore appearance and oiliness tend to shift gradually across several weeks of consistent morning and evening use, not immediately. Applying it inconsistently will slow that pace considerably compared with a steady routine.
Can I layer this serum with a retinoid or exfoliating acid?
This list does not include a retinoid or an exfoliating acid, so it is built as a standalone niacinamide step rather than a base formulated to carry either. Applying it after toner and letting it absorb before a separate treatment step is a reasonable order, but whether it pairs well with a specific acid or retinoid depends on that other product's own formula. Introduce anything new slowly and watch for irritation.
How do I verify this bottle is the authentic Korean-market Niacinamide 15 Serum?
The bottle carries its original Korean-market barcode, 8809598454637, unaltered from the release sold in Korea. COSRX verifies its own units directly rather than leaving that job to a reseller: enter the batch number and expiration date printed on your bottle into the verification page on cosrx.com. Reading those figures off your own bottle, not off a listing photo, is what actually confirms it.
Not on the ingredient list below: fragrance or parfum, denatured or SD alcohol, essential oils, silicones, parabens, sulfate surfactants, mineral oil or petrolatum and added color.
Full INCI (15): Water, Pentylene Glycol, Niacinamide, Butylene Glycol, Acetyl Glucosamine, 1,2-Hexanediol, Zinc PCA, Trehalose, Xanthan Gum, Pullulan, Allantoin, Ethylhexylglycerin, Sodium Phytate, Citric Acid, Tocopherol
Ingredient list read from incidecoder.com on 9 September 2026.
15 of 15 explained
- Water solvent
- Water is the base almost every serum, toner and cream is built on. It dissolves the water-loving ingredients and sets how light the finished texture feels. On an INCI list it is usually first, which only means it is the largest single ingredient by weight.
- Pentylene Glycol humectant
- Pentylene Glycol hydrates and, like the other longer-chain glycols, makes a formula less hospitable to microbes so the preservative system can be lighter. It also improves how evenly a product spreads.
- Niacinamide active
- Niacinamide is vitamin B3, and it is the most studied active in Korean formulation. It is used at roughly 2 to 5 percent for the look of uneven tone and visible pores, and it is water soluble, stable and comfortable beside almost every other active, which is why it turns up in so many lists.
- Butylene Glycol humectant
- Butylene Glycol is a small glycol that does two jobs at once: it holds water in the top layer of skin and it dissolves plant extracts and actives that plain water cannot. It also thins a formula, which is why watery Korean essences lean on it.
- Acetyl Glucosamine active
- Acetyl Glucosamine is the sugar unit hyaluronic acid is built from. It is used as a humectant and, at higher levels, for the look of uneven tone, often paired with niacinamide.
- 1,2-Hexanediol humectant
- 1,2-Hexanediol is a glycol used for two reasons: it holds water like glycerin, and it makes a formula harder for microbes to live in, so less traditional preservative is needed. Korean formulas use it heavily for that second reason.
- Zinc PCA active
- Zinc PCA pairs zinc with the humectant PCA. It is used in oily and blemish-prone formulas for the look of shine and visible pores, and it hydrates at the same time.
- Trehalose humectant
- Trehalose is a sugar that some desert plants use to survive drying out. In skincare it is a humectant that holds water in the outer layer and helps a formula feel comfortable rather than tight.
- Xanthan Gum thickener
- Xanthan Gum is a polysaccharide made by fermenting sugar. It thickens a watery formula into a gel and holds the whole thing in suspension so nothing separates. Too much of it and a serum turns stringy, which is why it appears in fractions of a percent.
- Pullulan film former
- Pullulan is a fermentation-derived polysaccharide that dries to a tight film, which is why it produces a temporary, visible tightening feel on the skin.
- Allantoin active
- Allantoin is a comfrey-derived compound used to condition skin and soften the outer layer so it feels smoother. It is one of the standard additions to a formula built for easily irritated skin.
- Ethylhexylglycerin preservative booster
- Ethylhexylglycerin softens skin and boosts a preservative system, which is why it is nearly always sitting beside phenoxyethanol or 1,2-hexanediol. It also cuts down the odour bacteria produce, so it turns up in deodorising products.
3 more explained
- Sodium Phytate chelator
- Sodium Phytate is a rice-derived chelator used in place of EDTA. It ties up trace metals so the formula stays stable and its colour and scent hold.
- Citric Acid pH adjuster
- Citric Acid is used in tiny amounts to bring a formula to the pH its actives need, not as an exfoliant at that level. It is an AHA, so at much higher concentrations it can also exfoliate.
- Tocopherol antioxidant
- Tocopherol is vitamin E. It is an oil-soluble antioxidant that protects the oils in a formula from going rancid and works on skin as an emollient, and it is regularly paired with vitamin C because each keeps the other going for longer.
- Market
- Korean market, the version sold in Korea
- EAN (barcode)
- 8809598454637
- Made in
- Republic of Korea
- Volume
- 20ml
- Category
- Serum & Ampoule / Pore-refining serum
- Actives
- Allantoin, Niacinamide, Trehalose, Zinc PCA
- Ships from
- California or Korea
Orders ship from California or direct from Korea with tracked delivery to your door, and both routes carry the same Korean-market release. Shipping is free on orders of $100 or more. Returns are accepted for 30 days, by mail.
We split shipments free, so one out-of-stock item never holds up the rest of your order.
Where this unit came from
- 1Seoul
Bought as Korean-market stock - 2Barcode
Listed against the Korean barcode on its box - 3California or Korea
Ships to you from either, as the same Korean-market release
We stock the version of a formula that is sold in Korea, not the release a brand prepares for another market under the same name. The barcode in the specification above is the Korean-market one and it is printed on the box you receive.
Every unit keeps its original barcode and batch code intact, so the unit in your hands can be checked against the brand’s own records.
Every order ships from California or direct from Korea, and returns run for 30 days.
Every claim on this page traces to the unit in the box, the barcode, the batch code and the price you can read for yourself.
Key benefits
- Niacinamide is third on the ingredient list.
- Zinc PCA and acetyl glucosamine support the pore-refining focus.
- Trehalose and allantoin round out the hydrating, calming base.
- No percentage is declared on this bottle's own list, so none is claimed.
Inside the formula
Inside the formula
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COSRX The Niacinamide 15 Serum
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COSRX, Korean-market original
Niacinamide Serum, 20 ml, with Zinc PCA.
Verify your unit when it arrives
Verify your unit when it arrives
Korean-market stock with the original barcode and batch code intact, exactly as it left Korea.
COSRX verifies units itself. Find the verification page on cosrx.com and enter the batch number and expiration date printed on your unit. Read them off the package rather than from us, which is the point.
Source: COSRX FAQ
On the unit itself
- The Korean-market barcode, unaltered from the retail package.
- The manufacturer’s batch code, exactly as the maker printed it.
정품Genuine article, Korean-market stock
What professionals say
What professionals say
What skin-care professionals say about skin care, quoted from the medical sources linked beside each.
Your skin barrier is basically your outer layer of the skin.
Melissa Piliang, MDDermatologist, Cleveland Clinic Pretty much every step of a Korean skin care routine is going to have some component of hydration.
Alok Vij, MDDermatologist, Cleveland Clinic
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