ABSTRACT
These words, written by Frazier and Blank in 1954, suggested that the external treatment of skin disorders in the mid-twentieth century was probably as haphazard as it was in ancient times. Now, some 40-plus years later, we have to ask ourselves, “Have things changed that much?” There have certainly been considerable advances in our understanding of the physicochemical properties of formulation systems and their ingredients, resulting in the ability to develop physically, chemically and biologically stable products which, after two or three years on the shelf, are as potent as they were when they were first manufactured. There have also been considerable advances in our knowledge of the skin and the processes which control the passage of chemicals across this unique biological stratum. In this instance, the ground rules were laid down by Scheuplein and Blank in the late 1960s and early 1970s (Scheuplein and Blank 1971), and these have been updated on a reasonably regular basis (Idson 1975; Barry 1983; Shah and Maibach 1993; Schaefer and Redelmeier 1996; Roberts and Walters 1998).
