1. What this serum is and what the numbers mean
The Ordinary Niacinamide 10% + Zinc 1% is a water-based serum combining 10% niacinamide with 1% zinc PCA, used to reduce the look of excess oil, visible pores and blemish-prone texture.
The percentages are concentrations of the two actives. Niacinamide is the amide form of vitamin B3. Zinc PCA is the zinc salt of pyrrolidone carboxylic acid, a compound naturally present in skin’s moisturising factor. On the ingredient list, niacinamide sits directly after water, which is consistent with a 10% inclusion. Zinc PCA appears further down, after the humectant pentylene glycol, which fits a figure at or below 1%. Ingredients are listed in descending order of concentration, and anything below 1% can be ordered freely.
On pH, niacinamide is stable across roughly pH 5 to 7. The formula is mildly acidic within that window. Labels rarely print pH, so read it from the brand’s product page instead of relying on a forum figure. It matters because very low or very high pH combined with heat can hydrolyse niacinamide to nicotinic acid, which can cause transient flushing.
The remaining ingredients are mostly supporting cast: pentylene glycol (a humectant and solvent), dimethyl isosorbide (a solvent that helps delivery), tamarind seed gum and xanthan gum (thickeners), and preservatives such as phenoxyethanol and chlorphenesin. There are no ceramides, fatty acids or occlusives, so this is not a moisturiser. Formulations are updated from time to time, so check the current list on your bottle.
2. What the evidence supports at 10%
Most clinical data on topical niacinamide come from concentrations between 2% and 5%, not 10%. That does not make 10% ineffective, but it means the extra concentration is an assumption rather than a demonstrated advantage.
- Sebum and oiliness: small vehicle-controlled studies, including work by Draelos and colleagues, found that 2% niacinamide reduced sebum excretion over several weeks.
- Acne-type blemishes: a trial from the 1990s found 4% niacinamide gel produced improvement comparable to 1% clindamycin gel over eight weeks in inflammatory acne. This supports niacinamide as a supportive ingredient. It does not make a cosmetic serum a treatment for moderate or severe acne.
- Uneven tone: studies of around 5% niacinamide over eight to twelve weeks reported reduced hyperpigmented spots, most likely by limiting melanosome transfer from melanocytes to skin cells. It does not stop melanin production.
- Barrier function: niacinamide has been shown to support ceramide and fatty acid synthesis and lower transepidermal water loss, which is why it is often well tolerated by oily skin that is still dehydrated.
The zinc component has a thinner evidence base. Oral zinc has some data in acne, and topical zinc salts are used for their sebum-regulating and mildly anti-inflammatory properties. Data on 1% zinc PCA alone are limited, so treat it as a plausible supporting ingredient. The visible effect you get is probably driven by the niacinamide.
On pores: pore size is largely set by genetics, sebum output and skin laxity. A serum can make pores look smaller by reducing oil and improving surface smoothness, but it cannot change their structure. Realistic assessment windows are eight to twelve weeks, not days.
3. Interactions with other actives
Niacinamide is among the more compatible actives, but three issues cause most real-world problems: outdated myths, stacked irritation, and hidden duplication.
- Vitamin C (L-ascorbic acid): the claim that the two neutralise each other or form irritating niacin comes from old in-vitro work at high heat and long exposure. At skin-care conditions the effect is negligible. The practical issue is that L-ascorbic acid at pH 3.5 or below, plus 10% niacinamide, can sting or flush sensitive skin. If that happens, use vitamin C in the morning and niacinamide at night. The brand has historically advised caution here, so check its current guidance.
- Retinoids (retinol, adapalene, tretinoin): compatible, and niacinamide may help buffer dryness. When starting a retinoid, introduce one product at a time rather than both in the same week.
- AHAs, BHAs and PHAs: chemically compatible. The risk is cumulative irritation, particularly with strong glycolic acid or a 2% salicylic acid leave-on. If your barrier feels tight, stinging or looks shiny and raw, drop one product rather than adding a moisturiser on top.
- Benzoyl peroxide and azelaic acid: both pair sensibly with niacinamide and are common in acne routines. Azelaic acid and niacinamide together are also a frequent choice for uneven tone.
- Other niacinamide products: many moisturisers, cleansers and sunscreens now contain 2% to 5% niacinamide. Layering several raises your total exposure well beyond 10% without you noticing.
That last point is where checking a formula against your whole routine helps. Scanning each product’s barcode in Skin Scan Genius shows where niacinamide or other actives overlap, so you can see stacking before it shows up as irritation.
4. Layering order and how to use it
Apply products from thinnest to thickest, water-based before oil-based. For this serum the sequence is: cleanse, then any acid toner or exfoliating treatment (give it a few minutes to settle), then the niacinamide serum, then other water-based serums such as hyaluronic acid, then moisturiser, and sunscreen in the morning. If you use a prescription retinoid at night, apply the niacinamide first and the retinoid after it, unless your prescriber has told you otherwise.
Use a few drops for the whole face. More does not mean better, and excess product is the main cause of pilling, where the serum’s gums and polymers ball up under moisturiser or sunscreen. Allow roughly a minute before the next layer, and avoid piling silicone-heavy primers on top.
Patch test first on the jawline or behind the ear for 48 hours. Begin with once daily, in the evening, for two weeks, then increase to morning and evening if skin is comfortable. Mild tingling can occur, but persistent burning, hives or flushing means stop using it. Oily and combination skin tends to tolerate 10% best. Dry, reactive or barrier-damaged skin may do better with a 2% to 5% niacinamide product.
Rosacea, eczema, perioral dermatitis, melasma and persistent or cystic acne are clinical conditions. A cosmetic serum is not a substitute for assessment, and niacinamide at this concentration may or may not suit them, so see a dermatologist first. If you are using this serum to target pigmentation, daily broad-spectrum sunscreen is non-negotiable, as UV will undo any gains. Before adding it to an existing routine, run the product through Skin Scan Genius to compare its actives with what you already use.
Check it against your own routine. Skin Scan Genius reads a product’s full INCI list and flags conflicts with the actives you already use, by skin type and concern.
Frequently asked questions
Can I use The Ordinary Niacinamide 10% + Zinc 1% with vitamin C?
Yes, for most people. The idea that they deactivate each other is largely a myth at normal skincare conditions. If low-pH L-ascorbic acid plus 10% niacinamide stings or flushes your skin, separate them, with vitamin C in the morning and niacinamide in the evening.
Does this serum cause purging?
Niacinamide is not an exfoliant, so true purging is unlikely. New breakouts after starting it are more often irritation, a reaction to another ingredient or product, or coincidence. If breakouts persist beyond four to six weeks, stop and consult a dermatologist.
Should I apply it in the morning or at night?
Either works. Morning use pairs well with sunscreen, particularly for tone concerns, while evening use is a gentler way to start. If you also use a retinoid or exfoliating acid at night, consider putting niacinamide in the morning to spread out the irritation load.
Is 10% niacinamide better than 5%?
Not proven. Most clinical studies used 2% to 5%, and higher concentrations raise the chance of irritation or flushing in some skin. If you are sensitive or new to niacinamide, a lower-strength product is a reasonable starting point.
