Dose response effect of chemical surface concentration on percutaneous penetration in human: In vivo + in vitro

The concentration of a formulation, defined as the mass of applied chemical per unit of skin surface area, is a key variable of skin absorption. Often only one concentration is available in the literature, hence a general evidence-based theory could allow prediction of how altering the concentration would produce a linear, increased, or decreased relative permeation. Here, we group topical chemicals into groups of how they permeate the skin when we increase or decrease their concentrations per unit area and discuss why we would like to predict their permeability in ranges of studied concentrations.