The influence of emollients on dermal and transdermal drug delivery

Emollients are widely used to supplement or replace sebum and provide skin repair and skin penetration enhancement. Their key function is to deliver a lipid film to the surface of the skin, which both lubricates the skin and provides a soothing action and, at the same time, retards transepidermal water loss, promoting skin hydration. An emollient is also characterized by its substantivity, that is, its ability to be retained by the skin after exposure to water, perspiration, friction, and other daily activities. A range of emollients exists, and these can both promote and retard skin penetration. However, in most cases, their effects are to promote skin penetration. There is an increasing need to have emollient products which prolong the skin retention but inhibit the skin penetration of certain actives, such as sunscreens. We also consider how practical formulation can be used to enable appropriate emollients and their formulations to provide both appropriate sensory softness and subtleness, but at the same time, appropriate control of the skin penetration of actives.