The effects of glycerol are discussed in detail. Glycerol can lead to a transition of crystalline lipid structures within the horny layer lipids into liquid crystalline states. Especially if applied in oil/water-emulsions it improves, the hydration of the horny layers better than urea. In addition, if facilitates the dissolution of desmosomes within the superior layers of the horny layer enhancing desquamation. Furthermore, by using glycerol, the mechanical properties of the skin can be influenced; long term used leads to increased elasticity. The roughness of the horny layer is reduced, which can be explained by the abrasive and/or the hydrating effect. Glycerol used in o/w-emulsions also protects against the influence of tensides or noxious lipophilic agents. Presumably a flux from the base of the epidermis towards its surface triggers the regeneration of the barrier. Finally, glycerol can lead--similarly to urea--to an improvement in active agent penetration, as has been proven for hexylnicotinate.