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J. Cosmet. Sci., 60, 359–363 (May/June 2009) 359 SCIENCE AND APPLICATIONS OF SKIN DELIVERY SYSTEMS, Johann W. Wiechers, Ed., (Allured Publishing Corp., Carol Stream, IL, 2008), 526 pp 14 pp. of color plates. As Dr. Wiechers explains in the preface, this book is intended to link information on delivery systems with the scientifi c un- derpinnings of their application. Formula- tors benefi t by knowing the potential applications as well as the limitations of each type of system and can therefore make an intelligent decision about which sys- tems are most likely to be of value in solv- ing a particular problem. The book is divided into fi ve parts. The fi rst deals with methodology for “Measur- ing Skin Delivery.” This is followed by “Skin Delivery from Emulsions,” Encapsu- lation Techniques,” “Alternate Ways to Enhance Skin Delivery,” and “Special De- livery Routes.” The fi rst chapter, by Dr. Wiechers, be- gins with an overview of the basics. There are short sections defi ning delivery, on why it is useful for cosmetics, and on routes of penetration and sites of action within the skin, as well as a brief overview of delivery systems. There is also a brief overview of in vitro and in vivo studies. This is followed by a chapter, also by Dr. Wiechers, which gives some additional details about mea- surement techniques. Chapter 3, by Walters and Brain, should be required reading for anyone who wishes to perform or interpret in vitro skin perme- ation experiments. Noting that there is generally good correlation between in vitro and in vivo data for specifi c compounds, the authors point out the need for additional data, particularly with respect to assessing the toxicological potential of cosmetic in- gredients. Among the issues with test pro- tocols is the need for testing on actual product formulations. Radiolabeled mate- rial facilitates analysis, but is nonspecifi c, i.e., impurities may carry the label and lead to misinterpretation of the data. Differ- ences between fi nite and infi nite dose regi- mens are described, and the need for proper selection of the type of application is em- phasized. As human skin is quite variable, suffi cient replicates should be performed to make statistically signifi cant comparisons (for example, of different formulations con- taining the same active) or to identify trends (for example, the relationship between mo- lecular weight and permeation). A section of the chapter describes stra- tum corneum skin stripping and the con- cerns with this technique. One problem is that successive strips do not remove equiva- lent amounts of the stratum corneum. It is common to plot the amount of permeant contained against the number of strips, but this does not show the relationship between permeation and stratum corneum depth. Furthermore, after reviewing the relevant literature, the authors conclude there is in- suffi cient correlative data available to vali- date skin stripping as a bioequivalence tool. The fi nal chapter in the methodology section, by Moore and Bi, is concerned with infrared spectroscopic techniques. This is a specialized technique requiring Book Reviews