Urea in skincare: why the percentage changes what it does

Most skincare ingredients do roughly the same thing at every strength — more of it, more of the effect. Urea does not work that way. Below about 10% it holds water in the skin. Above about 30% it takes the surface of the skin apart. Same molecule, opposite jobs.

This is why a 40% urea heel cream and a 5% urea body lotion are not the same product at different strengths, and why applying the first where you meant the second is a mistake people make regularly.

What urea is doing there in the first place

Urea is not a foreign substance being introduced to your skin. It is already there. It is one of the components of natural moisturising factor — the mixture of small water-binding molecules that healthy skin produces inside its own outermost layer to keep that layer supple. Skin that is chronically dry or rough tends to have less of it.

That gives urea an unusual position among actives: at low concentrations it is essentially topping up something the skin makes itself.

The three ranges

A 2021 review in Dermatology and Therapy (Piquero-Casals and colleagues) sets out the concentration bands that dermatology uses:

2–10% — humectant

In this range urea binds water into the stratum corneum and supports barrier function. It is a moisturiser, and it behaves like one: no peeling, no shedding, nothing dramatic. This is the range for everyday body creams, for skin that is dry rather than thickened, and for anyone who wants urea's hydration without its exfoliation.

10–30% — both at once

The middle band hydrates and softens keratin at the same time. This is where urea starts to be used for genuinely rough, thickened skin — the kind that has built up rather than merely dried out. It is also the range where the ingredient starts to be capable of stinging on skin that is already broken.

30% and above — keratolytic

At high concentrations urea denatures keratin by breaking the hydrogen bonds holding it together. The review describes this range as being for keratolysis and for debriding necrotic tissue. This is medical territory: hard heel fissures, thickened nails, hyperkeratotic plaques. It is not a moisturiser and it should not be treated as one.

The practical consequence: choosing a urea product means choosing a band, not choosing a brand. Work out whether your skin is dry or thickened first, then read the number.

How to read the number on the pack

Two things make the percentage harder to read than it looks.

The percentage often is not on the label at all. Under Article 19 of Regulation (EC) No 1223/2009, cosmetics sold in the EU must list ingredients in INCI names in descending order of weight down to 1% — but percentages themselves are not required. A brand that states one is choosing to. Where a product does not say, the position of Urea in the list is the only clue you have: near the front means a lot, after the preservatives means very little.

Urea and urea derivatives are different ingredients. INCI names like Hydroxyethyl Urea are urea-based humectants, not urea. They are used for water-binding, and they do not carry the high-concentration keratolytic behaviour described above. If the list says Hydroxyethyl Urea rather than Urea, you are looking at a hydration ingredient regardless of the number next to it.

Watch out too for Diazolidinyl Urea and Imidazolidinyl Urea. Despite the names, these are preservatives, present at fractions of a percent, and have nothing to do with urea's moisturising or keratolytic action.

Practical notes

• It stings on broken skin. Cracked heels and fissured fingertips are exactly the skin people reach for urea to fix, and exactly the skin that will burn when they apply it. Let the crack close first, then use urea to stop it coming back.
• Body strengths are not face strengths. Skin on the shins tolerates concentrations that skin on the cheeks does not.
• It stacks with occlusion. Urea holds water; something on top of it stops that water leaving. A urea cream under socks overnight does more than the same cream applied in the morning.
• It is not an acid. Urea is not an AHA or a BHA and does not work by lowering pH. It can generally be used alongside them, though on rough skin one active at a time is usually enough to see what is working.

Where our own product sits

Our UREVA™ Rough Skin Body Cream sits deliberately at the bottom of the range, and uses hydroxyethyl urea rather than urea itself — so it is a humectant formula, built for skin that is rough and dry rather than thickened. Panthenol, sodium hyaluronate and sodium PCA sit alongside it, and organic sunflower seed oil carries the whole thing. It is meant for elbows, knees, heels and shins, used daily, over months.

If what you have is hard, built-up skin that a 5% cream has not touched after a few weeks of consistent use, the honest answer is that you need a higher band than we make — and a pharmacist is the right person to point you at it.

Source

Piquero-Casals, J., Morgado-Carrasco, D., Granger, C., et al. (2021). Urea in Dermatology: A Review of its Emollient, Moisturizing, Keratolytic, Skin Barrier Enhancing and Antimicrobial Properties. Dermatology and Therapy, 11, 1905–1915.

This article is general information about cosmetic ingredients, not medical advice. Persistent or painful skin changes should be looked at by a doctor or pharmacist.