Skin accounts for approximately 15% of an adult s total body weight, with a surface of about 2m . It provides an entry and exit barrier to various substances, offers effective protection against harmful substances, microorganisms and ultraviolet radiation, and is also paramount in immunology and body homeostasis, preventing dehydration and loss of essential minerals.The topical route has a number of advantages over oral and parenteral routes: no first-pass metabolism, greater convenience resulting in better treatment compliance, lower side-effect frequency, and prompt dosing cessation if required. However, the stratum corneum allows penetration of only 1 to 5% of substances applied topically, making this application route much less efficient.