COSRX vs The Ordinary Niacinamide — Which Is Actually Better for Oily Skin?

Skincare · Serum Comparison

By Sarah Glow · Updated July 2026 · Medically reviewed by Dr. Lauren Kim, MD

COSRX vs The Ordinary Niacinamide — The Question Everyone Is Asking

If you have been researching the best niacinamide serum for oily skin, you have almost certainly ended up comparing these two. COSRX Niacinamide 15% and The Ordinary Niacinamide 10% + Zinc are the two most-purchased niacinamide serums globally — and they sit at very different price points and concentrations.

We tested both serums simultaneously on oily skin types over eight weeks, tracking oil production, pore visibility, skin texture, and tolerability. Here is exactly what we found — and which one is worth your money.

Quick Verdict — For Those Who Want the Answer Now

COSRX wins for results: Higher 15% concentration delivers faster, more visible reduction in shine and pore congestion. Worth the slightly higher price for oily skin.

The Ordinary wins for value: At ~$6 it delivers 80% of the results at 40% of the price. The best starting point for first-time niacinamide users or those on a budget.

Head to Head — Full Comparison

COSRX Niacinamide 15% Face Serum — Full Review

Price: ~$12 · Size: 20ml · Concentration: 15% niacinamide

COSRX built its cult following by making effective formulas at accessible prices. The 15% niacinamide serum is the highest-concentration option at this price point — and the texture is what sets it apart from every competitor. It is genuinely watery, absorbs in under 30 seconds, and leaves no residue at all. For oily skin users who have been burned by heavy serums that sit on top of skin or pill under foundation, this is a revelation.

Key Ingredients and What They Do

• Niacinamide 15% — regulates sebum, minimises pores, fades post-acne marks
• Panthenol (vitamin B5) — soothes and repairs the skin barrier
• Hyaluronic Acid — lightweight hydration without heaviness
• Arginine — amino acid that supports barrier function

8-week test result: Oil production visibly reduced by week 4. Mid-day shine noticeably less by week 6. Pore congestion improved significantly by week 8. No purging or irritation experienced at full 15% concentration on normal oily skin.

Pros and Cons

• Pros: Highest concentration at this price, ultra-lightweight texture, fragrance-free, absorbs instantly, works under all makeup types without pilling
• Cons: 15% may cause flushing in sensitive skin — introduce on alternate days for first two weeks. Smaller 20ml bottle runs out faster than The Ordinary 30ml

👉 Where to buy: Amazon · Olive Young

The Ordinary Niacinamide 10% + Zinc 1% — Full Review

Price: ~$6 · Size: 30ml · Concentration: 10% niacinamide + 1% zinc PCA

The product that made niacinamide a household name. At under $6 for 30ml, The Ordinary offers remarkable value — and the addition of zinc PCA is the formula’s real differentiator. Zinc PCA reduces sebum oxidation, which is the specific process that leads to blackheads and enlarged pores. For blackhead-prone oily skin specifically, this zinc combination outperforms niacinamide alone.

Key Ingredients and What They Do

• Niacinamide 10% — regulates sebum, minimises pores, fades hyperpigmentation
• Zinc PCA 1% — reduces sebum oxidation, directly targets blackhead formation
• No additional actives — clean, minimal, predictable formula

8-week test result: Blackhead reduction was the standout result — noticeably fewer by week 5. General shine reduction visible by week 4. Slightly slower than COSRX but delivered at a fraction of the price. One tester experienced slight pilling under silicone primer — resolved by waiting 60 seconds after application.

Pros and Cons

• Pros: Most affordable on the market, zinc PCA excellent for blackheads, larger 30ml bottle, beginner-friendly 10% concentration, widely available globally
• Cons: Slightly thicker texture can pill under silicone-based primers. 10% concentration delivers slower results than COSRX 15% for users wanting faster oil control

👉 Where to buy: Amazon · Sephora

Who Should Choose Which

Choose COSRX if:

• You have used niacinamide before and want stronger, faster results
• You need something that works seamlessly under makeup with zero pilling risk
• You want the fastest visible reduction in oily shine
• Your skin is not sensitive to higher concentrations

Choose The Ordinary if:

• You are new to niacinamide and want to start at a safer 10% concentration
• Blackheads are your primary concern — zinc PCA specifically targets these
• You are on a tight budget and want maximum product for minimum spend
• You have sensitive oily skin that may react to 15% concentration

Can you use both? Yes — some skincare users apply The Ordinary in the morning under SPF and COSRX at night for maximum overnight treatment. This gives you zinc benefits in the morning and higher concentration at night.

Are They Actually Comparable? The Concentration Question

COSRX has 15% niacinamide versus The Ordinary’s 10% — does this make COSRX automatically better? Not necessarily. Concentration is one factor but formulation matters enormously. The Ordinary’s zinc addition compensates for the lower concentration specifically for blackhead control. For overall sebum regulation, COSRX wins on concentration. For targeted blackhead treatment, The Ordinary’s zinc formula is the more specific tool.

Clinical research confirms that niacinamide at concentrations of 5% and above significantly reduces sebum excretion rates in oily skin. Both formulas exceed this threshold and deliver clinically meaningful results.

Think of it this way: COSRX is a higher-power general tool for all oily skin concerns. The Ordinary with zinc is a more targeted tool specifically for congested, blackhead-prone oily skin. Both are excellent — the right choice depends on your specific skin concern.

How to Use Either Serum Correctly

The application routine is identical for both serums:

1. Cleanser — morning and evening
2. Toner or essence — if using one
3. Niacinamide serum — 2-3 drops pressed gently into face and neck
4. Wait 60 seconds — especially important for The Ordinary under silicone primers
5. Moisturiser
6. SPF 30+ — morning only, non-negotiable

Important: Both serums are safe to use with retinol, vitamin C, AHAs, and BHAs. The old advice to avoid mixing niacinamide and vitamin C has been debunked by clinical research.

Frequently Asked Questions

Is COSRX or The Ordinary better for oily skin?

COSRX wins for overall oil control due to its higher 15% concentration. The Ordinary wins specifically for blackhead reduction thanks to the zinc PCA addition. For most oily skin users wanting general shine and pore improvement, COSRX delivers faster, more visible results.

Can I switch from The Ordinary to COSRX?

Yes. If you have been using The Ordinary at 10% without irritation you can switch to COSRX at 15% directly. Your skin is already accustomed to niacinamide so the higher concentration will not cause issues for most users.

Which absorbs better under makeup?

COSRX wins clearly. Its ultra-watery texture absorbs in under 30 seconds and never pills under any primer type. The Ordinary’s slightly thicker formula can pill under silicone-based primers if you apply the next step too quickly.

Is the price difference worth it?

COSRX costs about 3x more per ml than The Ordinary. Start with The Ordinary if budget is a concern — it delivers excellent results at a fraction of the price. Upgrade to COSRX if you want the fastest possible results or need a formula that works flawlessly under makeup.

Can I use both in the same routine?

Yes. Morning: The Ordinary under SPF. Evening: COSRX for maximum overnight treatment. This gives you the zinc benefits in the morning and higher concentration at night. Only recommended once your skin is accustomed to niacinamide.

The Verdict

COSRX wins overall for oily skin — the higher 15% concentration, ultra-lightweight texture, and flawless under-makeup performance make it the better daily serum for most oily skin types. The Ordinary wins on value and specifically on blackhead control thanks to its zinc PCA formula.

Our recommendation: if you have never used niacinamide before, start with The Ordinary. It is beginner-friendly, extremely affordable, and delivers real results. Once you are comfortable with niacinamide and want to level up, switch to COSRX for faster, stronger oil control.

Both products earn their place on our list of the best niacinamide serums for oily skin. Neither will disappoint — it is simply a question of what your skin needs right now.

Disclosure: This article contains affiliate links. WellGlowed may earn a small commission when you purchase through our links, at no additional cost to you. We only recommend products we have genuinely tested and believe in. This content is for informational purposes only and does not constitute medical advice. Consult a dermatologist for personalised skincare recommendations.