Glycerol as a skin barrier influencing humectant

Abstract

Glycerol, obtained mainly by saponification of oils and fats, is an important ingredient in pharmaceutical and cosmetic preparations. It acts as a humectant due mostly to its high hygroscopic property. Actually, endogenous glycerol in the skin is widely studied. The importance of endogenous glycerol is now established in the stratum corneum (SC) hydration. In humans, the glycerol skin content is correlated to sebaceous gland density. SC glycerol is mostly provided by triglycerides lipolysis in sebaceous gland and also sparsely by the breakdown of phospholipids by phospholipases. Glycerol diffuses from dermis and is transported into basal layers of the epidermis through aquaporin 3 (AQP3), a transmembrane water/glycerol transporting protein. Furthermore, AQP3-facilitated glycerol transport is involved in epidermal cell proliferation during repair of skin wounds. It is actually known that the skin care benefits of glycerol are due to different properties of the compounds: attraction of moisture, maintenance of crystallinity/fluidity of cell membranes and intracellular lipids, keratolytic effect, and its ability to diffuse and penetrate into the SC. Glycerol prevents damaging effect on the SC and leads to a more rapid reconstitution of the protective skin barrier following mechanical or chemical damage by generating stimulus for barrier repair. The water holding capacity of SC is related to hygroscopic compounds and to SC osmotic pressure. Glycerol could be helpful in atopic dermatitis treatment.