Studies on constituents of moisturizers: Water-binding properties of urea and NaCl in aqueous solutions

A water content of about 10% in the horny layer is necessary for softness a nd pliability of this part of the epidermis. In conditions with dry skin, e mollients of different types are used. It is important that solid data are collected about the effect of the ingredients of emollients and moisturizer s. Urea has since long been used in the treatment of dry skin. In the prese nt report, the mixture of urea and sodium chloride has been analyzed with r espect to its effect on the water vapor pressure in concentrated solutions. The depression of the water vapor pressure by NaCl and urea was found to b e additive. Thus, the decrease in water vapor pressure in aqueous solution of urea-NaCl mixtures can be estimated by adding the decrease of water vapo r pressure caused by dissolving the pure compounds. The results indicate th at urea and NaCl in aqueous solution do not interact strongly and are, ther efore, compatible in moisturizing preparations. They can, therefore, both b e expected to be effective in mixtures giving a better than one of them alo ne.