Galenical principles in skin protection

In recent years, dermatological formulations have progressed from an empirical art form to a more scientific discipline. Historically, clinical observations and controlled studies have demonstrated the markedly variable drug delivery potential of different topical vehicles. More recently, research efforts have focused on the role of drug uptake through appendages and the use of penetration enhancement systems (chemical and physical) to force chemicals through the skin. Much of this research has concerned the delivery of active drug moieties from specifically designed delivery vehicles or transdermal therapeutic systems to treat dermatological or systemic conditions. The complexity of topical dosage forms and of desired skin protection properties makes it difficult to formulate general guidelines for the development and the use of protective topical dermatological formulations. At present it appears that a product is designed for each specific environmental condition or threat. It seems unlikely that this will change until there are considerable advances in the engineering technology of topical formulations. At this point we still do not have a complete understanding of the function of topical products - especially the role of emerging theories like the 'metamorphosis' of the vehicle after application to the skin. In the immediate future it seems that totally occlusive vehicles will continue to be used to protect the skin, until chemical penetration enhancer or particulate-scavenging topical vehicles have been perfected and their toxicity has been fully evaluated.