ABSTRACT
The skin (cutis) is not only the largest organ, with a total weight around 3 kg and a surface of approximately 2.0m2 in humans, it is also the best and most easily accessible body part. Transcutaneous drug delivery has therefore been tried innumerable times. The problem with the approach is that most drugs cannot successfully diffuse through (permeate) intact skin. This is due to special structural, biochemical, and physiological properties of the organ, especially in its outermost 8-30mm thin layer (the stratum corneum), which has evolved into the primary skin barrier, one of the best in nature (Fig. 1, left).
