ABSTRACT
Over 4000 years ago the Egyptians used cosmetics, ointments and topical drugs for skin care, presumably on the assumption that these substances penetrated the skin layers, and yet until the turn of the century the skin has been regarded by scientists as being an effective impermeable membrane. For instance, in 1877 Fleischer 1 wrote that intact skin was totally impermeable to all substances. Today our understanding of the permeability barrier of skin is different from that of Fleischer’s era, and the recent development in transdermal delivery of nitroglycerin, anti-inflammatory agents and hormones for systemic therapy has established beyond any doubt that although the skin is one of the most impermeable body tissues, functioning as an effective barrier against water loss and the invasion of microorganisms and viruses, some drugs do penetrate through the intact skin and elicit systemic therapeutic effects.
