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INTRODUCTION

Activities:

Anti-inflammatory, hydrating, keratolytic

Important Chemical Components:

The chemical formula of urea (or carbamide) is CO(NH2)2.

Its molecular formula is CH4N2O.

Origin Classification:

Urea is a natural organic compound.

Personal Care Category:

Humectant, emollient

Recommended for the following Baumann Skin Types:

DRNT, DRNW, DRPT, and DRPW

SOURCE

Urea, the primary nitrogen-containing substance found in mammalian urine, is among the most commonly used humectant ingredients, along with glycerin, sorbitol, sodium hyaluronate, propylene glycol, α-hydroxy acids, and sugars (Table 28-1). It is a component of the natural moisturizing factor (NMF) and also exhibits a mild antipruritic effect.1 Urea in high concentrations (e.g., 40 percent) is effective as a hydrating and keratolytic agent in various cutaneous conditions including xerosis, psoriasis, onychomycosis and other nail disorders, ichthyosis, eczema, calluses, and corns.

HISTORY

Urea was first discovered in the 1700s in Europe. Its discovery is most often attributed to French chemist Hilaire Rouelle’s work in 1773, though Dutch scientist Herman Boerhaave is said to have first identified the compound as a major constituent of mammalian urine in 1727.2,3 German physician and chemist Friedrich Wöhler discovered, in 1828, that urea could be synthesized in vitro by combining the inorganic materials cyanic acid and ammonium without using any organic substances.2 This was the first credited laboratory synthesis of a naturally occurring organic compound.2 Interestingly, the chemical synthesis reported by Wöhler is not the chain of events that occurs in the mammalian liver to produce urea; the “urea cycle” was identified by German physician Hans A. Krebs and his medical student Kurt Henseleit in 1932.2 Urea has been used in hand creams since the 1940s.4 Thirty years later, urea in 20 percent concentrations was found to be effective in treating pruritus.5

TABLE 28-1Pros and Cons of Urea

CHEMISTRY

The urea molecule has two NH2 groups united with a carbonyl functional group. It acts as a physiological NMF.6

ORAL USES

Oral urea is used for some medical indications and has a long history of traditional folk medicine use, but this mode of administration is not thought to have appreciable cutaneous benefits.

TOPICAL USES

Twenty years ago, a double-blind, randomized comparison of two urea-containing creams revealed that 3 and 10 percent urea cream were equally effective in treating aspects of dry skin, particularly increasing hydration and decreasing scaling, and more effective than the vehicle control. Transepidermal water loss (TEWL) was unchanged after treatment with the 3 ...

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