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What Niacinamide Actually Does

4 July 2026 · 4 min read

Niacinamide is in almost everything now, which is usually a sign an ingredient is being oversold. In this case the claims mostly hold up.

Niacinamide — a form of vitamin B3, also called nicotinamide — has gone from a supporting ingredient to the headline on half the serums on the shelf. That kind of ubiquity usually means an ingredient is being stretched well past what it can do.

Niacinamide is an unusual case, because it genuinely does several distinct things and has reasonable evidence behind most of them.

What it does, with the evidence

It reduces sebum production. Studies have found measurable reductions in sebum excretion rates at around 2-4% concentration over four to eight weeks. For oily skin, especially in humid weather, this is the most immediately noticeable effect.

It fades pigmentation. Niacinamide interferes with the transfer of melanin from the cells that produce it to the surrounding skin cells. It does not stop melanin being made — it stops it arriving where you can see it. This makes it useful for post-inflammatory hyperpigmentation, the dark marks left behind after spots, which is one of the most common concerns on South Asian skin.

It supports the skin barrier. Niacinamide increases production of ceramides and other lipids in the outer layer. A stronger barrier means less water loss and less reactivity — which is why it helps skin that is both oily and irritated, a combination that otherwise has few good options.

It reduces redness. It is anti-inflammatory, and there is evidence for benefit in rosacea and in inflammatory acne.

It may help fine lines through effects on collagen production, though this evidence is weaker than the rest and improvements are modest.

The concentration question

Most of the research sits between 2% and 5%. That is the range where the benefits are documented.

Serums at 10% and above exist and are heavily marketed. There is little evidence that they do more, and there is reasonable evidence that they irritate more — flushing, tingling and redness are considerably more common at 10% than at 5%.

If you have used a 10% niacinamide serum and found it made your skin red or blotchy, you did not react badly to niacinamide. You reacted to too much of it. 5% is the sensible target, and 2-4% is plenty for oil control.

Who it suits

Niacinamide is one of the most broadly tolerated actives available. It works at skin-normal pH, it is stable, it does not increase sun sensitivity, and it plays well with almost everything.

It is a particularly good first active for:

• Oily or combination skin, especially in humid climates
• Post-acne marks
• Skin that is sensitive and cannot tolerate acids or retinoids
• Anyone whose barrier is compromised from over-exfoliating

It is a poor choice as a sole treatment for active cystic acne or for melasma, both of which need stronger intervention.

The vitamin C myth

You will still read that niacinamide and vitamin C cannot be used together — that they cancel each other out, or form nicotinic acid and cause flushing.

This comes from research conducted at high temperatures and unrealistic conditions, and it does not reflect how products behave on a face at room temperature. In practice, the two are used together in countless formulations without issue, and there is evidence they are complementary for pigmentation.

If you personally find the combination causes flushing — some people do — separate them: vitamin C in the morning, niacinamide at night. But there is no need to avoid the combination on principle.

How to use it

Either morning or night, after cleansing, before moisturiser. It is a water-based serum and sits early in the routine.

Start with once daily and build to twice if you want. Unlike retinoids and acids, there is no adjustment period to work through and no purging phase.

It layers comfortably under sunscreen and makeup, and it can be used alongside retinoids — in fact niacinamide's barrier support makes retinoid irritation more tolerable, which is a genuinely useful pairing.

What it will not do

It will not clear active acne on its own. It reduces oil and inflammation, which helps, but moderate to severe acne needs a retinoid, benzoyl peroxide, or a prescription.

It will not treat melasma. Melasma is driven substantially by UV and visible light, and the single most important intervention is rigorous daily sun protection.

It will not work quickly on pigmentation. Oil control shows up within a few weeks; pigmentation takes eight to twelve, and often longer.

The honest assessment

Niacinamide is a good, well-tolerated, moderately effective ingredient that does several useful things at once. That combination makes it an excellent default — the active most people should try first, and the one least likely to cause a problem.

It is not a replacement for sunscreen, and it is not a replacement for a retinoid if you need one. It is the sensible middle of a routine, which is a genuinely valuable thing to be.

Buy it at 5% or below, from a brand that lists the concentration, and give it two months.