Niacinamide: What It Is Good For, and What 10% Adds

Niacinamide is good for three things with trial support: lowering measured sebum, lightening some brown marks, and supporting the skin barrier. The trials used 2% to 5%, the pigment effect needed 5% and not 2% in the one study that compared them, and no efficacy trial above 5% turned up. The claim that it cancels out vitamin C rests on chemistry done under ultraviolet light and not on skin.

This article covers what niacinamide is, what the trials used, what each benefit rests on, why products climbed to 10% and 20%, and the vitamin C claim. It evaluates the evidence. It names no products and gives no routine.

The Most Agreeable Active

Niacinamide, also called nicotinamide, is the amide of vitamin B3. A 2021 review of its use for skin ageing and pigmentation states that, unlike nicotinic acid, it does not reduce cholesterol or cause flushing. It says cosmetics mainly formulate it at 4% to 5%, that it is well tolerated at those normal concentrations, and that no convincing evidence exists of a specific molecular target. The review's view is that it probably helps maintain skin homeostasis by regulating the redox status of cells.

A second narrative review lists the same mechanisms and states that clinical tests found no stinging up to 10% and no irritation up to 5%. Several of its authors are employed by companies named in its conflict statement. Much of the trial evidence also comes from industry-linked groups, so the benefits below are better read as trial results than as independent confirmations. Our article on serums sorted by what they target puts niacinamide among the better-supported serum ingredients.

What the Trials Used

The same 2021 review summarises the main trials, and the concentrations cluster tightly.

The review notes that in the dose-dependent study the effect was reversible: during the regression period the 5% result faded to the vehicle level after 42 weeks. Cosmetic formulation at 4% to 5% therefore matches where the trials sit.

Sebum

A pair of trials of 2% niacinamide (abstract) measured facial sebum. In 100 Japanese subjects in a double-blind placebo-controlled comparison, the sebum excretion rate was significantly lower after 2 and 4 weeks. In 30 Caucasian subjects in a 6-week split-face study, casual sebum level fell and the excretion rate did not significantly. The authors conclude it may lower excretion in Japanese individuals and casual sebum in Caucasian ones. The trials were run in Japan and the United States, and the abstract does not state funding.

The narrative review reports sebum reduction with 2% to 5% preparations and says the mechanism is unknown. Our article on why a face is oily covers what controls sebum and what does and does not change it.

Acne is where the reviews disagree. The narrative review describes proven clinical effectiveness against inflammatory acne. The Cochrane review of topical treatments for acne found four studies of nicotinamide against clindamycin or erythromycin, none of which measured participants' global assessment, and low-quality evidence of no difference in withdrawals or minor adverse events. It could not say whether nicotinamide treats acne as well as the antibiotics. A review of trials is the firmer of the two.

Pigment

The pigment mechanism is specific. The 2021 review says that in a single melanocyte culture nicotinamide has variable effects on melanin synthesis, and in co-cultures, reconstituted skin and living skin it consistently reduced pigmentation and slowed the transfer of melanosomes from melanocytes to skin cells. So it works downstream of the enzyme that hydroquinone and kojic acid target.

The trials suggest the strength matters. In the 79-woman study 5% worked and 2% did not significantly, and the effect faded after stopping. In melasma, the 27-woman trial of 4% niacinamide against 4% hydroquinone found all patients improved on both sides, with no statistical difference in colorimetry. Good-to-excellent improvement was seen in 44% on niacinamide and 55% on hydroquinone, and side effects in 18% against 29%. There was no vehicle arm and sunscreen was used throughout, so the trial shows two active creams performed similarly and cannot show how much of the change was niacinamide.

A sponsor-funded trial of 60 women with melasma tested a serum with 5% niacinamide, 1% tranexamic acid, 0.2% of a stabilised vitamin C derivative and hydroxy acids against 4% hydroquinone. Pigmentation fell significantly in both groups by three months and the serum was better tolerated. The mix of actives means the contribution of niacinamide cannot be isolated. Our article on removing dark spots covers where it fits.

Barrier

The barrier evidence is mostly cell work. The 2021 review reports that in cultured human keratinocytes nicotinamide raised the synthesis of ceramide, other sphingolipids, free fatty acids and cholesterol, and increased involucrin and filaggrin, and that a facial moisturiser with 2% nicotinamide improved the skin barrier in people with rosacea. It judges that nicotinamide could enhance the skin barrier's structure and function. That is a plausible mechanism with one clinical study behind the 2% figure. Our article on skin barrier repair covers what barrier repair needs.

Why the Percentage Kept Rising

No efficacy trial above 5% appears in the sources opened. The 2021 review says cosmetics mainly use 4% to 5%. The only 10% figure is a tolerability one: when 10% nicotinamide was applied, subjects did not feel stinging or flushing, and the irritation tests were run at 5%.

The idea that stronger products flush more is not supported by either review. The 2021 review says nicotinamide does not cause the flushing that nicotinic acid does, both reviews report no stinging up to 10%, and no source opened documents flushing from 10% or 20% products. What the sources do show is a gap: no trial tests whether 10% or 20% beats 5% for sebum or pigment. As reasoning, products climbed because a bigger number sells, not because a trial asked for it.

The practical reading is narrower than the headline. A 2% product may be below the strength that worked for pigment, and a 10% product may be above any strength shown to add benefit.

The Figure Audited: "Niacinamide and Vitamin C Cancel Each Other Out"

Verdict: unsupported as a claim about skin. A documented interaction exists under ultraviolet light in the laboratory. Findings:

A 2012 study of oil-in-water creams (abstract) exposed ascorbic acid with nicotinamide to ultraviolet light and found that nicotinamide acts as a photosensitiser for the photodegradation of ascorbic acid. The study measured loss under irradiation. It did not test storage in the dark or the pair on skin, and the work comes from one pharmaceutical group.

No trial in the sources opened compares the pair against each alone. The sponsor-funded 60-woman serum trial combined 5% niacinamide with a stabilised vitamin C derivative at 0.2%, and pigmentation fell and the serum was well tolerated. That shows the two can sit in one product and the combination can work. It does not say what either contributes, and a stabilised derivative is not L-ascorbic acid.

Some routine guides say niacinamide shifts the surface pH and leaves vitamin C inert, and our articles on layering order and on dark spots give versions of this sequencing advice. No source opened tests that. The 2021 review says only that nicotinamide can be combined with other active ingredients for added lightening efficacy. Our article on vitamin C serum stability covers what does affect vitamin C.

The limit: the UV chemistry shows an interaction can occur, and skin routines are not a UV lamp. An untested effect on skin is not a disproved one.

Conclusion

Niacinamide's reputation rests on trials at 2% to 5%. It lowered sebum in one trial pair, lightened brown marks at 5% and not at 2% in one study, and supports the barrier by a plausible mechanism with limited clinical data. Its acne evidence is thinner than its reputation, and nothing opened shows that 10% or 20% adds anything or that it cancels out vitamin C on skin.

If you start a niacinamide product, noting its percentage and photographing the same area in the same light each month, in an app like Skinic or in an album, shows more than the label does about whether it is doing anything. For pigment that is spreading or a mark that is changing, ask your own clinician.