Urea

What it is

Urea is a small nitrogen-containing molecule that the skin makes itself; it is one of the main constituents of natural moisturising factor (NMF), the mixture of water-binding compounds inside skin cells. Cosmetic urea is produced synthetically and is chemically identical. Its behaviour is strongly dose-dependent: low concentrations hydrate, while high concentrations loosen the bonds between dead skin cells.

What it does well

• Restores hydration in dry and scaly skin

  Because urea is part of the skin's own NMF, topping it up directly addresses one cause of dryness. Clinical trials show significant improvement in dry, scaly conditions including atopic dermatitis, ichthyosis and psoriasis.

  Strong evidence

• Softens and smooths rough, thickened skin at higher concentrations

  Above roughly 10% urea becomes keratolytic, breaking down the protein bonds that hold dead cells together. This is why it dominates heel and elbow creams. Face masks use far lower levels, where the effect is hydrating rather than exfoliating.

  Strong evidence

• Improves skin barrier function and has mild antimicrobial activity

  Urea influences the expression of genes involved in barrier lipid and antimicrobial peptide production, so its benefits go beyond simple water-binding.

  Moderate evidence

Worth knowing

• Can sting on broken or inflamed skin

  Urea is a well-known stinger on compromised skin: eczema flares, cracked skin, or freshly exfoliated areas. Reviews note that side effects are mild overall but become more frequent at high concentrations.

  Matters most toPeople applying it to actively inflamed eczema, cracked skin or skin that has just been exfoliated.

• Increases the penetration of other ingredients

  By loosening the outer layer, urea can help other actives get in more deeply. That is often useful, but it can also intensify the sting of an acid or retinoid used at the same time.

  Matters most toAnyone layering urea with exfoliating acids or retinoids.

Where the EU stands

Sources (2)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Urea in Dermatology: A Review of its Emollient, Moisturizing, Keratolytic, Skin Barrier Enhancing and Antimicrobial Properties

   Dermatology and Therapy (Heidelberg) · 2021 · doi:10.1007/s13555-021-00611-y

   Clinical trials show urea formulations significantly improve dry and scaly skin conditions, with mild side effects that become more frequent at high concentrations.

2. [2]
   A Biomimetic Combination of Actives Enhances Skin Hydration and Barrier Function via Modulation of Gene Expression: Results of Two Double-Blind, Vehicle-Controlled Clinical Studies

   Skin Pharmacology and Physiology · 2022

   Two vehicle-controlled clinical studies found that urea, described as the most prevalent natural moisturising factor, improved hydration and barrier function, with added benefit when combined with other NMF components.