Physical methods for studying stratum corneum lipids.

The skin's barrier to water loss and drug transport is closely related to the biophysical properties of the stratum corneum lipids. A number of in vitro and in vivo methods have been used to evaluate the physical properties of stratum corneum lipids. Two particularly useful techniques, infrared spectroscopy and differential scanning calorimetry, have provided a wealth of information about stratum corneum structure and function. The results of these studies demonstrate that the alteration of stratum corneum lipid packing results in increased skin permeability. Furthermore, the magnitude of increased permeability can be predicted from these physical properties. Therefore, these results provide both insight into the mechanism of transport through the stratum corneum, as well as a useful paradigm for selection of agents that reversibly alter the permeability of the skin.