Urea: The Moisturizer Your Skin Already Makes

It's not an active ingredient foreign to the epidermis. This small molecule is part of the natural moisturizing factor, the mixture the stratum corneum retains to keep its water. In cosmetics, it restores to dry skin what winter, hard water, and hot showers take away: suppleness, comfort, and softness on rough areas.

• INCI name Urea: molecule already present in the skin's natural moisturizing factor, where it accounts for about 7% (Rawlings & Harding, 2004).
• Its behavior changes with concentration: 2 to 5% for the face, 5 to 10% for the body, 10 to 20% for elbows and knees, 20 to 30% reserved for heels and soles of the feet — the table below details by zone.
• It should be applied to skin that is still damp, within 3 minutes of showering: this is when it retains the most water.
• At NOPAL LIFE, it works in tandem with prickly pear seed oil: one retains water, the other limits its evaporation.
• Three fields share the same name — cosmetics, medical biology, agronomy. Only the first is covered here: the disambiguation table below separates them.

Its formula involves only four elements: CH₄N₂O, or eight atoms in total — one carbon, one oxygen, four hydrogens, and two nitrogens. It is this richness in nitrogen that explains its parallel lives. In the body, the liver produces it at the end of the chain, when it converts ammonia resulting from the breakdown of proteins and amino acids into a stable and highly water-soluble compound. This cycle is even named after it — the urea cycle — and its function is clear: to neutralize ammonia, which cannot accumulate, into a molecule that the kidneys easily excrete. An adult thus eliminates about twenty to thirty grams per day through urine, which is the primary route for dietary nitrogen excretion.

It also holds a special place in the history of science: in 1828, the German chemist Friedrich Wöhler synthesized it in the laboratory from ammonium cyanate. This was the first time an organic compound was manufactured without recourse to living matter, and the idea of a "vital force" reserved for living beings never recovered. This date established synthetic organic chemistry.

Today's industrial production is based on the Bosch-Meiser process, patented in 1922: ammonia reacts with carbon dioxide under a pressure of about 150 bar, which first yields ammonium carbamate, which then dehydrates into urea and water. The carbon dioxide used is generally that captured upstream from the unit that produces ammonia — recycled carbon on-site rather than released. The quality intended for cosmetic products follows this same synthesis pathway, or uses biotechnology: no animal harvesting is involved, and the molecule obtained is strictly identical to what the skin produces.

From a regulatory perspective, it is identified by two stable identifiers — the INCI code Urea and the CAS number 57-13-6 — supplemented by an entry in the European CosIng inventory, under Regulation (EC) No 1223/2009 on cosmetic products. These, and not packaging promises, are what allow verifying that a product actually contains the molecule discussed on this page.

The stratum corneum is not just a simple waterproof barrier: each corneocyte contains a mixture of small molecules that are very water-hungry — amino acids, lactic acid, PCA, and urea — which dermatologists group under the name natural moisturizing factor. This mixture acts like a microscopic sponge: it captures water and holds it inside the skin, which maintains its suppleness even when the ambient air is dry (Rawlings & Harding, Dermatologic Therapy, 2004).

On dry skin, this reservoir of urea and amino acids is depleted. The result is visible and palpable: dull complexion, a feeling of tightness after showering, rough texture on shins, elbows, and heels. Applying a cream rich in humectants is like replenishing the sponge where there isn't enough — and urea has the advantage of being exactly the molecule the skin was already using.

At low concentrations, urea simply binds water. The higher the concentration, the more it softens the stack of dead surface cells: this is what gives the "smoothed heel" effect of highly concentrated balms. Hence the importance of choosing the right concentration for the area, rather than aiming for the highest percentage.

• Applying to perfectly dry skin. A humectant needs available water. On skin that has been wiped for twenty minutes in a heated room, it finds little.
• Transferring a "body" concentration to the face. A 20% balm designed for heels has no place on the cheeks: facial skin is much thinner, and comfort is achieved at much lower concentrations.
• Combining with an acid exfoliant on the same evening. At high concentrations, it is better to alternate evenings rather than layering.
• Forgetting the occlusive layer. Without oil or balm on top, the captured water eventually evaporates, especially in winter.

On damaged, irritated skin or skin with lesions, the advice of a healthcare professional takes precedence over any cosmetic routine.

Outside the bathroom, the same molecule has a far more massive career: it is the world's leading nitrogen fertilizer. Its richness in nitrogen — 46% of its mass, a record among common solid fertilizers — explains this success, as does its ease of transport and immediate dissolution in irrigation water. Spread in the field, it degrades under the action of a soil enzyme, urease, which releases nitrogen usable by the plant and carbon dioxide.

Second agricultural use: ruminant feed. Urea serves as a non-protein nitrogen source. The rumen flora degrades it into ammonia, which it reassembles into microbial proteins then digested by the animal — provided there is sufficient fermentable energy available, otherwise the nitrogen is lost. This is precisely what the PDI and PDIE nitrogen value systems established by INRAE quantify, which measure truly digestible proteins in the intestine rather than crude ingested nitrogen. A poorly managed urea solution in a ration also remains a classic cause of livestock accidents: here again, the dose is everything.

None of these uses are related to the tube on your shelf: cosmetic quality meets its own purity specifications.

This reference is cosmetic: it refers to the percentage of urea listed on a cream tube, not the values on a laboratory report. We do not publish any thresholds or interpretations here. A lab result should only be read with your doctor, who will put it into the context of your situation.