Ingredient Beauty BenefitsHumectant · Urea
Urea: a rare case where the concentration completely overrides the ingredient name
**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.
Last checked Sep 17, 2026
- In pregnancy
- Not established
- Irritation
- Low
- Daytime use
- ✓ Fine
Not a measurement — reported irritation grouped into five steps. It varies between people.
Urea is a component of the skin's own natural moisturising factor (NMF) — a substance already present in the stratum corneum.
For this ingredient, concentration matters far more than the name. That is a line this site repeats often, and urea is the most extreme case of it.
- Low concentrations (roughly below 10%): it draws and holds water. It works as a moisturiser.
- High concentrations (20–40%): it loosens the bonds between corneocytes and dissolves keratin. This is what goes on thickened heels.
Same name, different job. Read the concentration alongside every trial below.
Contents
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.
A 40% cream beat 12% ammonium lactate at two weeks
A 2002 randomised, double-blind, bilateral paired comparison. Twenty-five people being treated for moderate to severe xerosis took part and 18 completed the 28-day schedule. A 40% urea cream went on one side and a 12% ammonium lactate lotion on the other.
Assessment combined instrument measures (transepidermal water loss, skin capacitance, desquamation, roughness) with subject and investigator evaluation.
At day 14 the 40% urea cream was superior on roughness, fissure reduction, thickness and dryness. On most measures, improvement came faster with urea.
A few caveats belong with it. Twenty-five started and 18 finished. And the abstract names both products and their manufacturers outright — it helps to read this knowing it is one company's product measured against another's. The funding source is not stated, so we mark it unclear.
Also: this result is about 40%. The urea in an ordinary moisturiser is usually far below that.
- Randomised controlled trial in people · 25 participants · 4 weeks · Compared with another active ingredient · Funding not declared · Endpoint instrument measurement PMID 11978141
A 167-person trial — where the primary endpoint was missed
A 2017 randomised, double-blind, placebo-controlled study across 19 sites in France and Belgium. 167 people with diabetes and a deep open fissure on the heel used a cream containing urea, glycerine and petrolatum, or placebo, for four weeks.
The results in order:
- Primary endpoint (complete healing of the target fissure at 4 weeks): 46.3% against 33.3%. Not statistically significant (P = .088).
- Proportion still having a deep open fissure: 24.7% against 42.7% at 2 weeks (P = .027); 6.4% against 24.1% at 4 weeks (P = .002). Significant.
- Overall fissure healing: significant (P < .001).
- Xerosis improvement: significant (P < .001 at 2 weeks, P = .002 at 4).
How to read a trial whose primary endpoint failed is the point of this item. When the pre-specified primary outcome does not reach significance, the significant results that follow are read as a signal rather than a settled finding — because measuring many outcomes guarantees some will come out significant by chance.
That does not make the result meaningless either. The direction is consistent, it points the same way at both two and four weeks, and the sizes are clinically meaningful.
And this is not a trial of urea alone. The cream also contained glycerine and petrolatum. Which ingredient did the work, this trial cannot separate — the same structure seen on the glycerin page.
- Randomised controlled trial in people · 167 participants · 4 weeks · Compared with vehicle (same formula minus the active) · Funding not declared · Endpoint clinical events (cancers, lesion counts) PMID 28627029
20% urea and 30% aloe vera came out the same
A 2026 randomised trial in Indonesia in 35 patients with chronic kidney disease on haemodialysis. A 20% urea cream or a 30% aloe vera cream was applied to both arms for four weeks, with corneometer readings and an overall dry skin (ODS) score taken weekly.
Both creams significantly increased hydration and reduced the dryness score from baseline (p < .05). But no significant difference was found between the two (p > .05).
Thirty-five people cannot demonstrate 'no difference' — with a small sample, a real difference can easily fail to reach significance. So this result is not 'they are equal' but 'at this size we could not find a difference'.
The population matters too. Xerosis in dialysis patients has different causes, and the result does not transfer straight across to ordinary dry skin.
- Randomised controlled trial in people · 35 participants · 4 weeks · Compared with another active ingredient · Funding not declared · Endpoint instrument measurement PMID 42340432
In the Korean notice, urea names a product type rather than a restricted ingredient
Looking urea up in the Korean labelling notice puts it in a slightly unexpected place.
Regulation on Precautions for Use and Labelling of Allergenic Fragrance Ingredients, Annex 1, item 2, paragraph (a) — precautions by product type, entry 7:
Skin-softening products for hands and feet (hand creams and foot creams containing urea) a) Take care to avoid contact with eyes, nose or mouth b) Contains propylene glycol; use with caution if sensitive or with a history of allergy to it (labelled only on products containing propylene glycol)
Why that placement is unexpected: paragraph (b) of the same annex is where ingredients carrying their own restrictions live — salicylic acid, arbutin, AHAs, polyethoxylated retinamide and the rest. Urea is not there.
Instead, urea is used as the name that defines a product type, 'skin-softening products for hands and feet'. What the notice is regulating is not 'urea, a hazardous ingredient' but a category of keratin-softening products, and the precautions attached are about use — keep it out of eyes, nose and mouth — not about ingredient toxicity.
Worth adding: the ingredient that actually carries a warning in this entry is not urea. It is propylene glycol.
How to use it
- Read the concentration on the product first. A facial moisturiser and a heel product can share this ingredient and still be different objects.
- It is a humectant, so it goes on better while skin is still damp after washing.
- Reserve high concentrations for thickened skin. All the high-concentration data above comes from feet and hands.
- The trials above ran 2–4 weeks. This ingredient answers relatively quickly.
Cautions
- High concentrations sting on fissures or broken skin.
- As the notice requires, keep it away from eyes, nose and mouth.
- Some people react to the propylene glycol that often accompanies it; the notice requires a separate line for that ingredient.
- We found no established data on use during pregnancy.
- If you have diabetes and cracked feet, that is a clinical matter — fissures are an entry point for infection. That is precisely the situation the 2017 trial addressed.
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.
Related skin concerns
What this article relies on
- PubMed — 미국 국립의학도서관 문헌 데이터베이스National Library of Medicine · Checked on 2026-09-16
- 화장품 사용할 때의 주의사항 및 알레르기 유발성분 표시에 관한 규정 [별표 1] 화장품의 유형과 유형별·함유 성분별 사용할 때의 주의사항 표시 문구 — 식품의약품안전처고시 제2026-56호식품의약품안전처 · 시행 2026-08-05 · Checked on 2026-09-17