Dry skin is a common problem experienced by a vast majority of people. Moisturizers are commonly used to manage dry skin. Moisturizers are often used to replace skin’s natural oils, to cover tiny fissures in the skin, and to provide a protective film. They seem to slow down the evaporation of the skin’s moisture, and maintain hydration.1 On the basis of their action, moisturizers can be classified as occlusives, humectants, emollients and protein rejuvenators. Humectants include glycerin, sorbitol, urea, alpha hydroxy acids (i.e., lactic acid) and other sugars.1 Humectants attract water when applied to the skin and improve hydration of the stratum corneum.1

Glycerol, or glycerin, is an important component of pharmaceutical and cosmetic preparations. It acts as a humectant primarily on account of its high hygroscopic property.2 It occurs naturally in skin.2,3 Its role in skin hydration has been shown in experimental as well as human studies.3

Glycerol prevents damage to the stratum corneum and assists with to rapid reconstitution of the protective skin barrier after damage, whether mechanical or chemical.2 A randomized double-blind study, evaluated 197 patients with atopic dermatitis who were treated with either a moisturizing cream with 20% glycerin, its cream base without glycerin as placebo, or a cream with 4% urea and 4% sodium chloride. Adverse skin reactions such as smarting were felt significantly less among patients using the glycerin cream compared with the urea-saline cream. Glycerin containing cream seemed to be a suitable alternative to urea/sodium chloride in the treatment of atopic dry skin.4 Breternitz et al5 noted significant improvement in stratum corneum hydration and restoration of epidermal barrier function following treatment with glycerol-containing cream compared to the glycerol-free placebo.

Glycerin is a hygroscopic, nonvolatile, and viscous substance that is beneficial as a humectant. It is an effective moisturizer and humectant in cosmetic products and a potential skin protectant. It has the potential to hydrate the stratum corneum. It acts a humectant due to absorption of water from the atmosphere and it reduces the evaporation rate from the skin surface. The mode of action of glycerol both on stratum corneum hydration and barrier function is associated with the AQP3 channel.6

References

1. Lynde CW. Moisturizers: What They Are And How They Work. Skin Therapy Letter 2001;6(13). Available from: http://www.skintherapyletter.com/dry-skin/how-moisturizers-work/.
2. Roussel L, Atrux-Tallau N, Pirot F. Glycerol as a Skin Barrier Influencing Humectant. In: Lodén M, Maibach H (eds). Treatment of Dry Skin Syndrome. 2012; Springer, Berlin, Heidelberg.
3. Tucker R. What evidence is there for moisturizers? Available from: https://www.pharmaceutical-journal.com/files/rps-pjonline/pdf/pj20110416_cpd.pdf.
4. Lodén M, Andersson AC, Anderson C, et al. A double-blind study comparing the effect of glycerin and urea on dry, eczematous skin in atopic patients. Acta Derm Venereol. 2002;82(1):45-7.
5. Breternitz M, Kowatzki D, Langenauer M, et al. Placebo-controlled, double-blind, randomized, prospective study of a glycerol-based emollient on eczematous skin in atopic dermatitis: biophysical and clinical evaluation. Skin Pharmacol Physiol. 2008;21(1):39-45. Epub 2007 Nov 19.
6. Fluhr JW, Bornkessel A, Berardesca E. Glycerol — Just a Moisturizer? Biological and Biophysical Effects. Available from: http://www.scientificspectator.com/documents/personal%20care%20spectator/Glycerol%20a%20Moisturizer.pdf.