Tag: dark spots

  • Korea’s Nine Approved Brightening Actives: What the Human Studies Show for Melasma and Dark Spots

    Cover image for an article on the five ingredients to look for in melasma and dark spot care. Korea's functional cosmetics notification lists nine approved brightening actives with set concentrations, and this article reads the human studies for niacinamide, arbutin, magnesium ascorbyl phosphate and alpha-bisabolol, from Dr. J Ingredient Notes.

    🇰🇷 한국어판: 기미 화장품 성분 다섯 – 미백 고시 아홉 가지에서 고르는 법

    Hello, this is Dr. J. Today we are choosing brightening ingredients for melasma and dark spots the way a formulator does: from the regulation first, then from the human studies.

    Here is the part that surprises people outside Korea. In Korea, “brightening” is not a free marketing word. It is a functional claim, and there is an official list of actives with the amounts written next to them. The list has nine entries. I read the human evidence for each one, and I could open full abstracts for four. I will say that plainly as we go.

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    Primary sources

    📄 Regulation on Review of Functional Cosmetics, Annex 4 (MFDS notification) — the nine actives, their amounts, dosage forms and claim wording

    📄 Niacinamide and cutaneous pigmentation (Hakozaki 2002)

    📄 Arbutin 2.51% cream, 8 weeks (Morag 2015)

    📄 Magnesium ascorbyl phosphate and melanogenesis (Kameyama 1996)

    📄 Alpha-bisabolol in Asian women (Lee 2010)

    📄 EU SCCS opinion on alpha-arbutin and beta-arbutin (SCCS/1642/22, 31 January 2023)

    The Korean annex opens directly as an attachment file. It is worth opening once: the amounts are printed in a single line each, so you can hold the page next to a product’s back label.

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    In short, five lines

    ✔ Korea’s functional list has nine brightening actives, with the amounts fixed

    ✔ I could open full human-study abstracts for four of them

    ✔ Niacinamide separated from vehicle at 4 weeks, arbutin at 8 weeks

    ✔ The alpha-bisabolol trial was run on the back, not the face

    ✔ Tranexamic acid is not on the list, and its topical trials run 12 weeks

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    Nine actives, and what the amounts actually mean

    The annex is titled “Types of functional cosmetics for which data submission is omitted”. Read that title before you read the numbers. The concentrations are not upper safety limits. They are the amounts at which a company does not have to submit new efficacy data, because the authority has already accepted the evidence for that active at that amount.

    No. Active Amount Study opened here
    1 Broussonetia (mulberry) extract 2% —
    2 Arbutin 2–5% Morag 2015 · 102 women, 8 weeks
    3 Ethyl ascorbyl ether 1–2% —
    4 Oil-soluble licorice extract 0.05% —
    5 Ascorbyl glucoside 2% —
    6 Magnesium ascorbyl phosphate 3% Kameyama 1996 · 19 of 34
    7 Niacinamide 2–5% Hakozaki 2002 · 18 and 120 people
    8 Alpha-bisabolol 0.5% Lee 2010 · 28 women, 8 weeks
    9 Ascorbyl tetraisopalmitate 2% —

    The annex also fixes the dosage forms — lotion, liquid, cream and sheet mask — and the exact claim wording, which translates as “helps brighten the skin”. Even the directions are written down: apply an appropriate amount and spread evenly, and for a sheet mask, remove the sheet after 10 to 20 minutes and spread what is left. A product that follows all of this files a report instead of a full review.

    The five rows marked “—” are the ones where I could not open a human study abstract today. That is not the same as saying no study exists. It is a note about what I verified, and I would rather write it than leave you guessing.

    Evidence figure listing what the sources say about five brightening ingredients. First, Annex 4 of Korea's Regulation on Review of Functional Cosmetics lists nine approved actives: mulberry extract 2 percent, arbutin 2 to 5 percent, ethyl ascorbyl ether 1 to 2 percent, licorice extract 0.05 percent, ascorbyl glucoside 2 percent, magnesium ascorbyl phosphate 3 percent, niacinamide 2 to 5 percent, alpha-bisabolol 0.5 percent and ascorbyl tetraisopalmitate 2 percent, in lotion, liquid, cream and sheet mask forms. Second, the niacinamide study had 18 people use 5 percent and vehicle in a paired design and 120 tanned people use three treatments, with pigmentation falling after 4 weeks, Hakozaki 2002. Third, the arbutin 2.51 percent cream study randomised 102 women to 54 active and 48 placebo for 8 weeks, with lightening in 75.86 percent of melasma cases, Morag 2015. Fourth, magnesium ascorbyl phosphate improved 19 of 34 people with pigmentation and only 3 of 25 with normal skin, Kameyama 1996. Fifth, alpha-bisabolol was applied for 8 weeks on the back rather than the face by 28 women, Lee 2010.

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    The four, in one table — including what each was compared with

    A percentage means very little on its own. What it was measured against is where the value sits: the same cream without the active, a different product, untreated skin, or simply the starting point.

    Active Study People · duration Compared with What was found
    Niacinamide 5% Hakozaki et al. 2002 18 with hyperpigmentation vehicle moisturiser, paired on the same person Significant drop in pigmentation and rise in lightness at 4 weeks
    Niacinamide 2%
    with sunscreen    		 same paper 120 with facial tanning vehicle, sunscreen alone Better than vehicle on skin colour measures
    Arbutin 2.51% Morag et al. 2015 102 women · 8 weeks
    54 active · 48 placebo    		 placebo cream, double-blind Lightening in 75.86% of melasma, 56.00% of solar lentigo
    placebo figures not in the abstract
    Magnesium ascorbyl phosphate Kameyama et al. 1996 34 with pigmentation
    duration not in the abstract    		 baseline pigmentation 19 of 34 improved significantly · 3 of 25 with normal skin
    Alpha-bisabolol
    concentration not in the abstract    		 Lee et al. 2010 28 women · 8 weeks · back vehicle cream on the same women Significant lightening in most subjects
    Tranexamic acid
    not on the list    		 covered in guide 9 trials run 12 weeks varies by trial Topical-only results were not statistically clear

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    Niacinamide 2–5% — the point where it separated from vehicle was 4 weeks

    Hakozaki 2002 carried two human trials in one paper. In the first, 18 people with facial hyperpigmentation used a 5% niacinamide moisturiser and a vehicle moisturiser in a paired design — both products on the same face, one per side. In the second, 120 people with facial tanning were each assigned two of three treatments: vehicle, sunscreen, or 2% niacinamide plus sunscreen.

    Changes were quantified by computer analysis of high-resolution facial images and by visual grading. After 4 weeks, niacinamide significantly decreased hyperpigmentation and increased skin lightness compared with vehicle alone. The paired design is the part I like: season, sleep and sun exposure are held constant because both sides belong to the same person.

    The same paper ran cell work. Niacinamide gave 35–68% inhibition of melanosome transfer in a keratinocyte and melanocyte co-culture, and reduced pigmentation in a reconstructed epidermis model. It had no effect on mushroom tyrosinase activity or on melanin production in cultured melanocytes. Worth keeping those in their own lane: a co-culture is not a face, and I would not carry the 35–68% figure over to what happens on your cheek.

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    Arbutin 2–5% — 102 women, 8 weeks, and a different number in the EU

    Morag 2015 was a double-blind, placebo-controlled randomised trial in 102 women aged 26 to 55 with melasma or solar lentigo. Fifty-four used a cream containing 2.51% arbutin twice daily for 8 weeks; 48 used placebo.

    Lightening was seen in 75.86% of the melasma cases and 56.00% of the solar lentigo cases. The placebo-arm figures are not given in the abstract, so I have not carried them over. Read the percentage as “how many in the active arm showed lightening”, not as “how much better than placebo”.

    Europe looked at the same molecule from the safety side, which is a different question from efficacy. The SCCS adopted its opinion on 31 January 2023.

    What the number decides Korea · Annex 4 EU · SCCS/1642/22 (2023)
    Nature of the figure efficacy data can be omitted safety assessment
    Arbutin (beta) 2–5% safe in face creams up to 7%
    Alpha-arbutin not named in the annex safe in face creams up to 2%, body lotions up to 0.5%
    Hydroquinone content not the subject of this annex “as low as possible… not higher than the unavoidable traces in both arbutins”
    LOQ 3 ppm · LOD 1 ppm

    So a Korean product and a European product can both be correct and still print different percentages, because the two numbers answer different questions. And on a back label, “arbutin” and “alpha-arbutin” are two different names — the annex lists the first one. Guide 15 goes through that comparison in detail.

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    Vitamin C derivatives — 19 of 34, and only 3 of 25

    Four of the nine entries are vitamin C derivatives: ethyl ascorbyl ether 1–2%, ascorbyl glucoside 2%, magnesium ascorbyl phosphate 3% and ascorbyl tetraisopalmitate 2%. Pure ascorbic acid is unstable in a finished formula, so the molecule is modified and the skin’s enzymes are expected to release it.

    Of those four, the one I could open was magnesium ascorbyl phosphate. Kameyama 1996 reported that 19 of 34 patients with chloasma or senile freckles showed significant lightening. In the same paper, among 25 people with normal skin, only 3 did.

    Put those two numbers side by side and you get a way to read them: this is an ingredient that earns its place where the pigment already is. Expect it to work on the dark patch rather than to change your overall complexion. The trial duration is not stated in the abstract, which is worth knowing before you set a deadline for it.

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    Alpha-bisabolol 0.5% — the trial was not run on faces

    Lee 2010 tested a base cream containing alpha-bisabolol on 28 female subjects, applied once a day for 8 weeks. The application site was pigmented skin on the back, and the same women also applied a vehicle control cream. Results were assessed by clinical and biophysical methods, and after 8 weeks most subjects showed significant lightening.

    Two honest notes. The concentration of alpha-bisabolol in the cream is not given in the abstract, and the back is not the face: thicker stratum corneum, different sun exposure, different pigment history. The annex figure of 0.5% is what Korea accepted for the claim; the trial figure is simply not stated. Knowing that keeps the expectation the right size.

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    The one that is not on the list — tranexamic acid

    Tranexamic acid does not appear among the nine. A Korean product carrying the brightening claim with tranexamic acid has therefore been through an individual review with its own safety and efficacy dossier, rather than the report route that the listed actives allow.

    The trials are built around 12 weeks, and when the topical route is pooled on its own the result was not statistically clear. Guide 9 sets out those numbers, including the confidence interval, and it is the honest place to start if a tranexamic acid serum is already in your routine.

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    What is not in this article, and why

    ✔ Comparisons with hydroquinone or prescription creams — a cosmetics article should not line itself up against a drug

    ✔ Laser and chemical peel trials — procedures are a separate conversation from ingredients

    ✔ Retinol for pigmentation (Kafi 2007) — I opened the abstract and it reports fine wrinkles and collagen markers, with no pigmentation outcome, so it is out

    ✔ Mechanism paragraphs — where I could not open the review, I stopped at what the abstract itself states

    ✔ Claims that circulate online — “vitamin C erases melasma”, “use brighteners at night only” — no primary source, so no sentence

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    Four things to check when you buy

    ✔ Whether the carton carries the functional cosmetics mark, with the claim wording printed underneath in the same size or larger

    ✔ Which of the nine names appears in the ingredient list

    ✔ Whether the format is a lotion, liquid, cream or sheet mask

    ✔ Whether there is enough product for 4 to 12 weeks, since that is the length the trials ran

    Whichever active you choose, daytime sunscreen travels with it. Pigment darkens again in sunlight, and the 120-person arm of Hakozaki 2002 was itself run on top of a sunscreen. Guide 11 covers how to read SPF and PA labels.

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    One line

    Pick a name from the list of nine, give it 4 to 12 weeks, and wear sunscreen while you do.

    The next guide takes on organic and natural cosmetic labelling — what those words are allowed to certify under the Korean standard.

    📌 Related guides

    📌 Niacinamide: How Much Is Enough (Guide 2)

    📌 Arbutin vs Alpha-Arbutin: Korea’s 2–5% and the EU limits (Guide 15)

    📌 Tranexamic Acid Cream: What the Melasma Trials Found (Guide 9)

    📌 Adenosine 0.04%: Who Decided That Number (Guide 12)

    📌 How to Read a Korean Cosmetic Ingredient List (Guide 14)

    📌 Sunscreen SPF and PA: How to Read the Numbers (Guide 11)

    About the author · Dr. J

    MS in Veterinary Medicine, PhD in Life Sciences. I worked as a researcher at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) and now run Beaurea, a cosmetics manufacturing company, where I write the formulas myself. This blog reads the research papers and the regulatory documents and turns them into plain-language criteria for choosing ingredients. I don’t recommend specific products here – only criteria that apply to any product.

    📄 References

    · Regulation on Review of Functional Cosmetics, Annex 4 — Types of functional cosmetics for which data submission is omitted (MFDS notification)

    · Hakozaki T, Minwalla L, Zhuang J, et al. Br J Dermatol 2002;147(1):20-31

    · Morag M, Nawrot J, Siatkowski I, et al. J Cosmet Dermatol 2015;14(3):185-190

    · Kameyama K, Sakai C, Kondoh S, et al. J Am Acad Dermatol 1996;34(1):29-33

    · Lee J, Jun H, Jung E, et al. Int J Cosmet Sci 2010;32(4):299-303

    · SCCS Opinion on alpha-Arbutin and beta-Arbutin, SCCS/1642/22, adopted 31 January 2023

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    This article summarises a public regulation and published research. It is information, not a diagnosis or a treatment plan. The figures are as written in the notification and in each abstract, and results differ from person to person. If a pigment change worries you, please speak with a professional.

    — Dr. J Ingredient Notes

  • Tranexamic Acid Cream: What the Melasma Trials Found – Alone, With Niacinamide, and Why 12 Weeks (Ingredient Guide 9)

    Cover image for Ingredient Guide 9 on tranexamic acid: a signal blocker rather than a pigment eraser, 2 to 5 percent in cosmetics, a 12-week split-face trial in 50 people with melasma and a 667-person meta-analysis. Dr. J Ingredient Notes.

    Hello, this is Dr. J.

    Ingredient Guide number nine is tranexamic acid – a name that now shows up on the back of many dark-spot and melasma products.

    Here is the surprising part. This ingredient started life as a drug that stops bleeding. This post follows how an operating-room molecule ended up in a melasma cream, and then looks at how far the topical trials actually go.

    The short version: it works on its own, but the numbers are steadier with niacinamide, and the benchmark is 12 weeks.

    🇰🇷 Read this in Korean: 트라넥삼산 크림, 기미 연구가 확인한 것 (성분 백과 ⑨)

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    📄 Read the sources first

    · Kim HJ et al., Acta Derm Venereol 2017 – meta-analysis of 11 studies, 667 participants (open access)

    · Ebrahimi B et al., J Res Med Sci 2014 – 3% cream, 50 patients, 12 weeks, split-face

    · Hsin et al., Cosmetics 2024 – 3% cream and serum, 22 patients, 8 weeks (open access)

    · Korea’s functional-cosmetic review rules – listed ingredients vs. individual review (Korean)

    · 🏠 COSMILE Europe INCI database – type the name exactly as it appears on the label

    The meta-analysis reports topical, oral and injected tranexamic acid separately. This post uses the topical numbers.

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    15-second summary · no sound

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    The four lines, if you are in a hurry

    ✔ Tranexamic acid does not erase melanin. It turns down the signal that tells skin to make more

    ✔ Cosmetics typically use 2–5%. In Korea it is not on the official whitening-ingredient list, so a “whitening” claim means the product passed an individual review

    ✔ 50 people with melasma applied a 3% cream for 12 weeks: their melasma score (MASI) fell significantly

    ✔ Across 11 studies and 667 people, topical use alone is still thinly supported – it works on its own, but the results are steadier with niacinamide

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    How it works – not an eraser, a signal blocker

    When skin is hit by UV, the surface cells (keratinocytes) use an enzyme called plasmin to send melanocytes a “make more pigment” message. Melasma is close to that message being stuck on in one patch of skin.

    ✔ Tranexamic acid blocks plasmin – the same action it has as an anti-bleeding drug

    ✔ So unlike vitamin C, which works on pigment that is already there, it slows down new pigment

    ✔ That is why results take time. Nearly every trial runs 12 weeks

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    How to read the numbers – 2%, 3%, 5% and the “whitening” claim

    The trials used 2%, 3% and 5%, and a 2024 review treats 2–5% as the usual range. On a Korean label, though, the claim tells you more than the percentage. Korea has a regulatory category called “functional cosmetics”: a product may print “whitening” only if it uses an ingredient on the MFDS list at the listed level, or passes an individual review with safety and efficacy data. Tranexamic acid is not on that list.

    What you see on the label What it means
    “Whitening functional cosmetic” claim Because tranexamic acid is not a listed ingredient, the product had to pass an individual MFDS review (safety, efficacy and human-test data) to carry this claim
    No claim · contains tranexamic acid A regular cosmetic. The ingredient is there, but the product may not say “whitening”
    Whitening claim + niacinamide, arbutin, etc. The claim may rest on a listed ingredient (niacinamide, arbutin, alpha-bisabolol, licorice extract and others) filed without review. Tranexamic acid is along for the ride
    A percentage (2% · 3% · 5%) Inside the trial range is fine. With no percentage, the position on the ingredient list is your clue – higher means more; ingredients at 1% or below may be listed in any order

    In short, a “whitening” claim means reviewed, not stronger. And no claim does not mean the ingredient is idle – for that, look at the trials below. Other countries regulate claims differently; the studies themselves are the same everywhere.

    Tranexamic acid evidence summary. 50 people with melasma applied a 3 percent cream to one side of the face for 12 weeks and the melasma score MASI fell significantly with fewer side effects than the prescription comparator, Journal of Research in Medical Sciences 2014. A meta-analysis of 11 studies and 667 people found MASI fell by 1.60 overall but only 1.36 for topical use alone, not statistically significant, Acta Dermato-Venereologica 2017. 22 people used a 3 percent cream and serum with niacinamide for 8 weeks and dark-spot color fell 13 percent, Cosmetics 2024. Tranexamic acid is not on Korea's listed whitening ingredients, so a whitening claim means an individual review.

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    What the research found – 50 people for 12 weeks, a 667-person meta-analysis, 22 people for 8 weeks

    First, 50 people with melasma. Each person applied a 3% tranexamic acid cream to one side of the face and a prescription combination to the other, for 12 weeks. Both sides improved significantly on the melasma score (MASI), with no difference between them. Side effects were significantly fewer on the tranexamic acid side (P=0.01) – Ebrahimi et al., J Res Med Sci 2014.

    Second, the 667-person meta-analysis. Pooling 11 studies, tranexamic acid overall lowered MASI by 1.60 (p<0.001). But topical use alone came to 1.36 – not quite statistically solid (p=0.08), because the individual studies disagreed with each other. Side effects were mild: redness, irritation, dryness – Kim HJ et al., Acta Derm Venereol 2017.

    Third, 22 people for 8 weeks. Adults aged 45–67 used a 3% tranexamic acid cream and serum that also contained 5% niacinamide, for 8 weeks. Dark-spot color intensity fell 13% (significant), spot size fell 6%, and 77% said their spots looked lighter. No serious adverse effects – Hsin et al., Cosmetics 2024.

    Study People · duration What was used What was found
    Ebrahimi 2014 50 · 12 weeks 3% cream alone (split-face) MASI fell significantly · fewer side effects
    Kim 2017 meta-analysis 11 studies · 667 Topical, oral and injected pooled Overall −1.60 (p<0.001) · topical alone −1.36 (p=0.08)
    Hsin 2024 22 · 8 weeks 3% + 5% niacinamide, cream and serum Spot color −13% · 77% reported lighter spots

    Put the three side by side and this is what they say. Tranexamic acid works on its own, but the studies vary enough that it is too early to call the topical evidence settled. The study that paired it with niacinamide produced steadier numbers. Using the two together is closer to what the research has seen. And every trial ran 8–12 weeks – it is not an ingredient to judge after a few days. Oral tranexamic acid and in-office procedures are outside the scope of this post.

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    How to use it – order and pairing

    ✔ Morning and night, right after cleansing, on the spots first, then moisturizer

    ✔ Niacinamide can be in the same product or the same routine – that is the pairing the trial used

    ✔ Vitamin C (the “eraser” side) fits in the same routine too – vitamin C in the morning, tranexamic acid at night is one easy split

    ✔ It is gentle enough that you rarely need to alternate days with retinol or AHAs. If that night stings, move tranexamic acid to the morning

    ✔ Sunscreen in the morning is half the job. This ingredient slows the signal; if UV keeps sending it, you stay where you started

    ✔ Oral tranexamic acid is a prescription drug. It is a separate conversation from cosmetics

    The ingredient compatibility chart shows which pairs can share a night and which should be split.

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    Five things to check before you buy

    ✔ Is the percentage printed? – 2–5% is the trial range

    ✔ Is there a “whitening” or brightening claim? – in Korea that means a review was passed. Without it, the ingredient still works

    ✔ Is niacinamide in the formula? – that is the pairing the trial used

    ✔ Where does tranexamic acid sit on the list? – higher means more

    ✔ Is there enough for 12 weeks? – this is not an ingredient to judge in under 8 weeks

    Save these five lines for the store. Reading the back takes about five minutes.

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    In one line

    🧪 Tranexamic acid slows the signal that tells skin to make pigment. It works on its own, but with niacinamide, over 12 weeks, and under sunscreen is where the research has seen it do best.

    Next in the Ingredient Guide: peptides (Guide 10) – many names, uneven evidence, so I will take them one name at a time.

    📌 Earlier posts

    · Retinol: Start at 0.1% – How to Read the Concentration Numbers (Ingredient Guide 1)

    · Skincare Ingredient Compatibility Chart – 12 Ingredients, What to Layer and What to Split

    · Dull, Rough Skin? Glycolic Acid (AHA) – What the Research Shows and How Much Is Safe

    · Salicylic Acid (BHA): 0.5% vs 2%, Explained (Ingredient Guide 8)

    About the author · Dr. J

    MS in Veterinary Medicine, PhD in Life Sciences. I worked as a researcher at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) and now run Beaurea, a cosmetics manufacturing company, where I write the formulas myself. This blog reads the research papers and the regulatory documents and turns them into plain-language criteria for choosing ingredients. I don’t recommend specific products here – only criteria that apply to any product.

    📄 References

    · Kim HJ et al., Acta Derm Venereol 2017 – Efficacy and safety of tranexamic acid in melasma: a meta-analysis and systematic review (11 studies, 667 participants)

    · Ebrahimi B, Fatemi Naeini F, J Res Med Sci 2014 – Topical tranexamic acid as a promising treatment for melasma (3% cream, 50 patients, 12 weeks)

    · Hsin et al., Cosmetics 2024;11(5):168 – 3% tranexamic acid cream and serum with niacinamide, 22 patients, 8 weeks

    · Korea Cosmetics Act, Article 4 – functional-cosmetic review and listed ingredients

    This post summarizes published research and public documents for information only. It is not a substitute for diagnosis or treatment. If you have a concern, please consult a professional.

    — Dr. J Ingredient Notes

  • Niacinamide: 5% Is Enough – What Each Concentration Has Actually Shown (Ingredient Encyclopedia 2)

    Niacinamide: 5% is enough - human studies ran at 2-5%, Korea's whitening functional range is 2-5%, no evidence 10% or 20% works better, Dr. J Ingredient Notes cover

    🇰🇷 이 글의 한국어판 → 한국어판

    Hello, I’m Dr. J.
    In Korea you can hardly walk past a serum shelf without seeing niacinamide on the label.
    It sits in most products approved here as brightening functional cosmetics.

    The number next to it keeps changing, though: 2%, 5%, 10%, 20%.
    Does a bigger number buy you more?
    Here is what the human studies actually support.

     

    The short version

    ✔ Niacinamide is a form of vitamin B3. One ingredient works on dark spots, pores, acne, redness, fine lines and the skin barrier
    ✔ The human studies ran at 2-5%, and Korea’s brightening functional range is also 2-5%
    ✔ No head-to-head human study shows 10% or 20% doing more. The chance of flushing does go up
    ✔ Morning and night are both fine, and it layers with retinol, vitamin C and acids
    ✔ Expect the first change around week 4 and a clear one at 8-12 weeks. Consistency matters more than strength
     

    What the research confirms – five jobs, one ingredient

    Niacinamide by concentration - 2% less sebum (Draelos 2006), 4% acne (Shalita 1995) and melasma (Navarrete-Solis 2011), 5% pigment, lines and redness (Bissett 2005, Hakozaki 2002), 10% no added benefit, 20% flushing
    · Dark spots — it blocks the hand-off of melanin to skin cells. It leaves the pigment-making enzyme alone, which is why it is gentle. Blotches faded over 8 weeks at 5%
    · Fine lines, redness, elasticity — 50 people used 5% on one half of the face and a plain cream on the other for 12 weeks. Fine lines, blotches, red spots, sallowness and elasticity all improved
    · Acne — a 4% gel matched a 1% clindamycin (antibiotic) gel over 8 weeks in 76 people
    · Sebum and pores — 2% for 4 weeks lowered sebum output. Less oil, less prominent pores
    · Barrier and dryness — it raises ceramide synthesis, so the skin loses less water. That is why it buffers a retinol or acid routine

    There is a melasma study too.
    4% niacinamide matched 4% hydroquinone with fewer side effects (27 people, 8 weeks).

     

    Choosing the number: 2, 5, 10 or 20%

    · 2% — the sebum and pore studies. A sensible starting point for sensitive skin
    · 4% — the acne and melasma studies
    · 5% — pigment, fine lines and redness. This is the reference point
    · 10% — no human comparison showing it beats 5%. More people report flushing
    · 20% — it exists on shelves, the evidence does not, and stinging is common

    That warm flush some people feel comes less from niacinamide itself than from nicotinic acid left in the raw material.
    A safety review of high-purity material (CIR) found no irritation even at 10%.
    Still, nothing shows that more is better, so 5% used for a long time is the path the research supports.

     

    Three things to check on the label

    ✔ Is there a number? “Contains niacinamide” can mean 0.5%
    ✔ A brightening functional claim (Korea) means 2-5% is definitely in there. It does not mean high strength
    ✔ If your face flushes, drop the strength or change products. Purity differs, so two 5% products can feel different
     

    When to use it, and what it layers with

    ✔ Morning and night — it is stable in light. Apply at the serum step, moisturiser on top
    ✔ With retinol → yes. It cushions the dryness and stinging of the break-in weeks
    ✔ With vitamin C → yes. The “never together” rule traces back to a 1960s solution experiment, not to modern formulas
    ✔ With AHA or BHA → yes. Applied after an acid it helps the barrier recover
    ✔ Give it 4 weeks, then keep going to 8-12 — the pigment-transfer block reverses within days of stopping, so it is an ingredient you stay on

    🧪 Check niacinamide pairings in the ingredient checker

     

    One line

    Niacinamide: 5%, morning and night, 8-12 weeks.
    It covers dark spots, pores, redness and the barrier at once and gets along with everything else, which makes it a good default serum in a routine.

    ▶ Ingredient encyclopedia 1: Retinol: Start at 0.1% – How to Read the Concentration Numbers
    ▶ Ingredient encyclopedia 3: Bakuchiol vs Retinol – What a 44-Person Trial Found
    ▶ Earlier post: Skincare Ingredient Compatibility Chart – What to Layer and What to Split
    ▶ Earlier post: Not All Vitamin C Serums Work – 3 Conditions the Research Says You Need
    🇰🇷 이 글의 한국어판 → 한국어판

    About the author · Dr. J
    MS in Veterinary Medicine, PhD in Life Sciences. I worked as a researcher at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) and now run Beaurea, a cosmetics manufacturing company, where I write the formulas myself. This blog reads the research papers and the regulatory documents and turns them into plain-language criteria for choosing ingredients. I don’t recommend specific products here – only criteria that apply to any product.

    References
    1. Korea MFDS, Regulation on the Review of Functional Cosmetics, Table 4 — brightening: niacinamide 2-5%
    2. Bissett DL et al. Dermatologic Surgery 2005;31:860-865 — 5%, 50 subjects, 12 weeks, split-face
    3. Hakozaki T et al. British Journal of Dermatology 2002;147:20-31 — melanosome transfer reduced 35-68%, 5% for 8 weeks
    4. Shalita AR et al. International Journal of Dermatology 1995;34:434-437 — 4% vs 1% clindamycin, 76 subjects, 8 weeks
    5. Draelos ZD et al. Journal of Cosmetic and Laser Therapy 2006;8:96-101 — 2%, sebum output
    6. Navarrete-Solís J et al. Dermatology Research and Practice 2011 — 4% vs 4% hydroquinone, 27 subjects, 8 weeks
    7. Tanno O et al. British Journal of Dermatology 2000;143:524-531 — ceramide and barrier lipid synthesis

    ※ This article is general information. Results vary with individual skin. It does not recommend or criticise any specific product. If you are being treated for a skin condition, talk to your dermatologist first. The author runs a company that manufactures and sells cosmetics.