Urea

What the evidence says

Urea is part of the skin's natural moisturizing factor. At concentrations of about 10% or less it mainly acts as a humectant; above 10% it increasingly softens and breaks down thick scale, which is why stronger preparations are used for callus, keratoderma, or very scaly disease rather than routine facial moisturizing.^[1][2]

A systematic review of moisturizers for foot xerosis found urea was the most studied ingredient, but study quality and outcome variation prevented a firm ranking. A broader moisturizer review found clinical effects better documented for urea and glycerin than for several other highlighted ingredients, while still noting limited direct comparisons.^[3][4]

A newer systematic review covering ichthyosis, atopic dermatitis, psoriasis, and other conditions reported improvements in dryness, scale, erythema, and transepidermal water loss across 31 selected studies. This supports usefulness across scaly disorders but does not establish one concentration or vehicle for every diagnosis.^[5]

Stinging and burning become more likely as concentration rises or when the product is applied to fissured, inflamed, or freshly shaved skin. High-strength urea should be kept away from eyes and sensitive mucosa; persistent irritation is a reason to reduce strength, frequency, or stop.^[2][1]