In the work, impact of aqueous 40%-ethanol solution on the transepidermal transport of photodynamic dye indocyanine green has been studied with backscattering spectroscopy. It has been first obtained the value of the dye diffusion coefficient through the stratum corneum ex vivo at the use of ethanol as a diffusion enhancer: (6.85±3.75)×10−7 cm2/s.