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Ingredient Beauty Benefits

Skin concerns

Texture and flaking

Built-up dead cells and rough skin surface.

Start here

What it is

Skin that is uneven to the touch and does not reflect light evenly. Not one disease but an appearance with several causes layered together.

Why it happens

Keratin builds unevenly, pores stand out, and fine lines and small scars mix in.

Where to start

Start by asking what is blurring the surface. If it is keratin, the acids; if pores, the pores page; if scars, the scars page. This concern splits.

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

Texture is the concern where concentration and pH completely override the name of the ingredient.

Urea is the most extreme case. At low concentrations it holds water; at 20–40% it dissolves keratin. Same name, different object.

And with acids the label gives you a hint. A Korean notice fixes the wording for AHA-containing products, so the line advising you to consult a specialist means the product is above 10% or below pH 3.5. The glycolic acid page explains it in detail. Gluconolactone, though, does not carry that line — because it is not an AHA.

Evidence level
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 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 evidenceHumectant

Urea

Urea

5% and 40% are effectively different products. At low concentrations it holds water; at high concentrations it dissolves keratin. A 40% cream beat 12% ammonium lactate at two weeks, and in a 167-person trial of a urea-containing cream the primary endpoint was missed (P = .088) while the other measures were significant.

Moderate evidenceAcid

Gluconolactone (PHA)

Gluconolactone

A 1997 trial put four acids side by side and then challenged the skin. Sites treated with gluconolactone lost significantly less barrier function than vehicle, than untreated skin, and than glycolic acid. And the Korean AHA warning text does not apply to this ingredient.

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 evidenceBarrier lipid

Petrolatum

Petrolatum

A 1997 study proposed using petrolatum as the standard reference substance in irritation testing. And in a 2000 trial comparing 'skin-identical lipids' with pure petrolatum, there was no indication the lipids did better. Recorded here as a case where the expensive ingredient did not beat the cheap one.

Moderate evidenceAntioxidant

Alpha-lipoic acid

Thioctic Acid

One trial: 33 people applied a 5% cream to one half of the face and its vehicle to the other for 12 weeks. Laser profilometry showed roughness falling 50.8% versus 40.7%, a significant difference (P < .001). The 40.7% on the placebo side has to be read alongside it.

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.

Not establishedRetinoid⚠ In pregnancy Do not use

Hydroxypinacolone retinoate

Hydroxypinacolone Retinoate

The human material we found is one 8-week study of a serum containing retinol, HPR, peptides and silybin. And that abstract states neither the number of participants nor a control group. All the authors work at one cosmetics company's research centre. There is no trial of HPR alone on this page.

Clinical procedures related to this concern

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