8.3.1.2　The structure of the skin

The efficiency of TDD depends on the integrity of the skin barrier，whether the skin is hyperkeratotic，or the arrangement and fluidity of the skin structure molecules.For example，in diseases where the skin barrier is damaged（e.g.，atopic dermatitis），the transdermal efficiency of drugs is enhanced.However，it decreases in hyperkeratotic diseases（e.g.，corns，calluses，and tinea pedis）due to the thickened stratum corneum.Besides，when various internal and external factors lead to changes in the arrangement structure and fluidity of proteins and lipid molecules in stratum corneum，the skin permeability will also change accordingly.(https://www.daowen.com)