Antioxidant · Niacinamide

Niacinamide: a 50-person trial showed improvement, but the control was a moisturiser

In a 12-week split-face study of 50 people, 5% niacinamide reduced fine lines, yellowing, red blotchiness and pigmented spots. The control was not nothing but the same moisturiser, and the manufacturer paid for the trial.

Last checked Sep 16, 2026

In pregnancy: Not established
Irritation: Low
Daytime use: ✓ Fine

Not a measurement — reported irritation grouped into five steps. It varies between people.

Korean classification Listed functional-cosmetic activeVerified against: 기능성화장품 심사에 관한 규정 [별표 4] 자료제출이 생략되는 기능성화장품의 종류 — 식품의약품안전처고시 제2025-88호 · Checked on 2026-09-16Listed amount 2~5% · As a percentage 2–5%

Niacinamide is a form of vitamin B3 and, in Korea, a listed active for whitening claims. It irritates little, so it goes into almost everything — and attracts a matching amount of exaggeration.

The numbers below come from a single trial. That it is a single trial is exactly why this ingredient does not move above 'moderate'.

Contents

Fine lines, yellowing, red blotchiness and spots decreased — 50 people, 12 weeks
The Korean listed amount for whitening is 2 to 5%
We could not find the basis for the claim that it must not be used with vitamin C

What is established

The same ingredient at a different strength, in a different formula, is a different product. These are the conditions the studies used.

Moderate evidenceConcentration studied 5% · cream

Fine lines, yellowing, red blotchiness and spots decreased — 50 people, 12 weeks

Fifty women aged 40 to 60 took part in a 12-week double-blind split-face study. One side received a moisturiser; the other received the same moisturiser with 5% niacinamide added. Yellowing, wrinkling, red blotchiness and hyperpigmented spots improved more on the niacinamide side.

Two things belong together here. First, the control was a moisturiser rather than no treatment — that is the stronger design. Second, the authors worked for the manufacturer (P&G). That does not make the result wrong, but a single manufacturer-funded trial cannot carry a 'strong evidence' label.

Randomised controlled trial in people · 50 participants · 12 weeks · Compared with a plain moisturiser · Funding manufacturer-funded · Endpoint scores from blinded assessors PMID 18492135

Ingredient dataConcentration studied 2–5%

The Korean listed amount for whitening is 2 to 5%

Annex 4 of the Regulation on the Review of Functional Cosmetics sets niacinamide at 2 to 5%. Within that range a product can be filed for a whitening claim without submitting its own data.

The 5% used in the trial sits at the top of that range. Products at 10% are common, but there is no evidence that exceeding the listed range scales the benefit, and reports of irritation go up.

기능성화장품 심사에 관한 규정 [별표 4] 자료제출이 생략되는 기능성화장품의 종류 — 식품의약품안전처고시 제2025-88호

Not establishedConcentration studied — Not established

We could not find the basis for the claim that it must not be used with vitamin C

The claim is widespread, but we found no trial showing that this combination causes a problem on human skin (PubMed, checked 16 September 2026).

Not established means neither safe nor risky. If evidence turns up, this entry and its level will change.

How to use it

Morning or evening, either works. It is not especially light-sensitive.
Raising the concentration does not raise the benefit proportionally. The evidence above comes from a 5% trial.
A serum or a cream is fine, as long as it stays on. Rinse-off products are a different question from the trial above.

Cautions

Redness or stinging is occasionally reported, more often with high-concentration products.
We found no established data on use during pregnancy. Ask a doctor or pharmacist if you need a decision.
A 'whitening functional cosmetic' label means the product completed its filing, not how much of the ingredient it contains.

With a new ingredient, apply a small amount somewhere inconspicuous, such as the inner arm, for two days first. Stop if it reddens or stings.