The determination of a diffusional pathlength through the stratum corneum.

The stratum corneum possesses a very heterogenous structure. As such a diffusing molecule can access a number of different pathways. It is probable that the excellent barrier properties of the stratum corneum result from a tortuous diffusional pathway around the dead cells. However, there are considerable problems in designing diffusion experiments and analysing the data to prove, without doubt, which is the predominant pathway. The mathematical problems posed are discussed in this article.