Structural determinants of the response of the skin to chemical irritants.

A study was made of the relationships between structural parameters of the epidermis and stratum corneum and the skin's sensitivities to chemical irritation by dithranol or ammonium hydroxide. Statistically significant positive correlations were found between the minimal blistering time to ammonium hydroxide and the area bounded by the skin surface contour line as determined by a skin surface replica technique. A significant positive correlation was also found between the minimal irritancy dose of dithranol and (a) the mean corneocyte area, and (b) the mean epidermal thickness in cell numbers. Mean corneocyte area was also found to increase with age and to be significantly less in UV-sensitive Types I and II subjects than in the relatively UV-insensitive Types III and IV subjects. These correlations are further evidence that there are inherent structural differences in the skin which influence the way the skin reacts to chemical trauma.