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Skin concerns

Pigmentation

Melasma, freckles and marks that stay behind.

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What it is

Skin pigment darkening unevenly. Melasma, freckles, sun spots and acne marks all fall here, but they are different things.

Why it happens

Pigment-making cells are provoked into making more, and it moves up into the outer layers and stays. What provokes them differs — sun, inflammation, hormones.

Where to start

Sunscreen comes before any ingredient. Melasma responds to light, and without that step the rest largely returns to where it started.

There are no numbers and no citations in this box. What has been established, and how far, is below.

One thing about pigmentation has a clear order: sunscreen comes before any active. Melasma responds to light, and without that step the rest mostly returns to where it started.

This is a rare concern where the ingredient and procedure layers confirm each other. On the tranexamic acid page we wrote that the topical route was not significant and only the oral route was. And in the 39-study network meta-analysis on the laser toning page, second place went to oral tranexamic acid.

First place in that analysis was not laser alone either — it was laser plus a topical.

Evidence level
Strong evidenceUV filter

Sunscreen

An ingredient class — not a single line on an ingredient list

An Australian trial randomised 1,621 people and followed them 4.5 years. Squamous cell tumour incidence was 39% lower (1,115 vs 1,832 per 100,000); basal cell carcinoma showed no difference. This is one of the few entries on this site carrying strong evidence.

Moderate evidenceRetinoid⚠ In pregnancy Do not use

Retinol

Retinol

In a vehicle-controlled trial, 0.4% retinol applied for 24 weeks moved the fine-wrinkle score by −1.64 against −0.08 for vehicle. Thirty-six people, and it was forearms, not faces. In pregnancy, guidance says do not use it.

Moderate evidenceAntioxidant

Niacinamide

Niacinamide

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.

Moderate evidenceAcid

Salicylic acid

Salicylic Acid

Most acne trials used 30% peels performed in a clinic. What Korea allows as an acne functional claim is 0.5%, and only in rinse-off cleansers. There is a sixtyfold gap between those two numbers.

Moderate evidenceAntioxidant

Vitamin C (ascorbic acid)

Ascorbic Acid

In pig skin, L-ascorbic acid entered only when formulated below pH 3.5, and 20% was the concentration for optimal absorption. Pure ascorbic acid is not among Korea's listed whitening actives; four of its derivatives are.

Moderate evidenceAntioxidant

Bakuchiol

Bakuchiol

In a 12-week double-blind trial of 44 people, bakuchiol 0.5% and retinol 0.5% reduced wrinkle area and hyperpigmentation to a similar degree, with more irritation on the retinol side. With no vehicle arm, the trial cannot say what the improvement on either side was due to.

Moderate evidenceAcid

Glycolic acid (AHA)

Glycolic Acid

In a 22-week, 74-person, vehicle-controlled double-blind trial, 76% of people using 8% glycolic acid cream improved by at least one grade of photodamage (vehicle: 40%). Thirty years on, we found nothing better for this ingredient. And the same molecule did not protect the skin barrier.

Moderate evidenceOther

Tranexamic acid

Tranexamic Acid

In a 2024 meta-analysis of 28 randomised trials, topical tranexamic acid produced no significant difference over existing treatment at either 8 or 12 weeks. The oral route did. Same molecule, different route, different conclusion.

Moderate evidenceAcid

Lactic acid

Lactic Acid

In a 1983 trial, a 12% lactate lotion, a 5% lactic acid lotion and a plain emollient all three significantly improved xerosis. The difference emerged one to two weeks after treatment stopped. And in the 1996 photodamage trial it beat vehicle on four forearm measures — more than glycolic acid managed in the same trial.

Moderate evidenceRetinoid⚠ In pregnancy Do not use

Retinaldehyde

Retinal

In a randomised double-blind trial comparing 0.1% and 0.05% creams in 40 Korean women over 13 weeks, there was no statistically significant difference between the two concentrations. Note what the trial lacks: there was no vehicle arm — everyone applied retinaldehyde. A comparison against applying nothing is not here.

Moderate evidenceAntioxidant

Cysteamine

Cysteamine HCl

A 2024 meta-analysis pooled seven randomised controlled trials. Cysteamine 5% significantly reduced melasma scores versus placebo (SMD −0.84, 95% CI −1.19 to −0.49, I² = 0%) and showed no significant difference against hydroquinone 4% (SMD 0.16, P = .42). The individual trials, though, ran 20 to 40 people.

Moderate evidenceOther

Kojic acid

Kojic Acid

In a 1999 split-face trial, a gel containing 2% hydroquinone and 10% glycolic acid went on both sides of the face, and kojic acid 2% was added to one side only. More than half the melasma cleared in 60% on the kojic side and 47.5% on the other. But that base gel cannot be bought as a cosmetic in Korea — hydroquinone is prescription-only.

Moderate evidenceAntioxidant

Ferulic acid

Ferulic Acid

In two randomised, double-blind, placebo-controlled trials, the side treated with a vitamin C, E and ferulic acid serum did significantly better than the placebo-serum side on wrinkles and elasticity (at 12 weeks, 23.9% versus 6.8%, P < .001). The designs are among the best in this layer. But what was tested was a serum containing three ingredients, and both sides of the face had a procedure first.

Moderate evidenceOther

Thiamidol

Isobutylamido Thiazolyl Resorcinol

Two randomised trials compared 0.2% thiamidol against its own vehicle and both lowered melasma scores significantly (36.1% vs 16.1% over 12 weeks in 200 people). In the same trial, though, freckles and solar lentigines showed no difference, and the 24-week trial found that once people stopped, they matched the vehicle group.

Moderate evidenceAntioxidant

Glutathione

Glutathione

In a 46-person split-face comparison, topical glutathione lowered the melanin index more than placebo. In a separate 83-person, 12-week oral trial, the difference from placebo was not statistically significant. A 2025 systematic review points at the gap between how much this is used and what has been shown.

Moderate evidenceHumectant

N-acetyl glucosamine

Acetyl Glucosamine

In a double-blind, vehicle-controlled trial in 202 women, all four measures were significantly better (P < 0.05). But what that trial looked at was 2% NAG together with 4% niacinamide. A trial of NAG alone exists, but its abstract gives no participant count. And both trials list a manufacturer among the authors' affiliations — so they cannot pass this site's condition for 'strong evidence' at all.

Moderate evidenceOther

4-Butylresorcinol

4-Butylresorcinol

A 20-person split-face trial of a 0.1% cream and a 45-person trial of a dissolving microneedle patch. Both compared against the same formulation with only this ingredient removed, and both saw melanin index fall significantly by week 8. The trials are small.

Early researchAcid

Mandelic acid

Mandelic Acid

A 50-person randomised trial compared a 45% mandelic acid peel against a 30% salicylic acid peel over 12 weeks. Overall acne score improvement did not differ, but salicylic acid did better on non-inflammatory lesions and mandelic acid on inflammatory ones. And adverse effects were fewer with mandelic acid. But nothing was left untreated.

Early researchOther

Arbutin

Arbutin

The Korean listed amount is 2–5%. In a split-face pilot in 30 people with melasma, alpha-arbutin 5% plus kojic acid 2% did not differ from a prescription triple-combination cream on objective measures, and relapse was worse on the triple-combination side.

Early researchAntioxidant

Polypodium leucotomos

Polypodium Leucotomos Extract

This is swallowed. In a placebo-controlled trial in healthy adults, fewer people had sunburn episodes (2 vs 8) and more had a raised redness threshold (8 vs 1). But the abstract does not give a total number of participants, and it reports outcomes as counts of people rather than means. And this ingredient's clearest trial, by numbers and design, was not cosmetic at all — it was an add-on to phototherapy for vitiligo.

Early researchOther

Hexylresorcinol

Hexylresorcinol

The trial on this ingredient has the design this site keeps wishing for — the control was not a vehicle but niacinamide alone. Randomised, double-blind, split-face, over 12 weeks, the combination beat niacinamide alone significantly on pigment spots (L*), fine lines and skin firmness. But all the authors are at the manufacturer's research arm, and the abstract gives no participant count.

Early researchAntioxidant

Pycnogenol

Pinus Pinaster Bark Extract

This is swallowed. In a randomised, double-blind, placebo-controlled trial in 44 women with melasma, mMASI fell 49% (placebo: 34%). The difference was significant. But both arms also used a triple combination cream and a sunscreen. So what the trial shows is not what pycnogenol does on its own, but what it adds on top of a treatment that already works.

Ingredient dataSoothing

Alpha-bisabolol

Bisabolol

The Korean listed amount is 0.5%, the lowest of the nine whitening actives. But we could find no human trial comparing this ingredient on its own against vehicle. What turns up are studies of multi-ingredient formulas.

Medicines used for this concern

Medicines are not listed alongside cosmetic ingredients. Dosage and whether a prescription is needed are settled in consultation.

Clinical procedures related to this concern

Procedures are not listed alongside topical ingredients. They are not something you use at home.