A series of sulfonamide compounds, para-aminohippurate, and inulin were used to study the permeability of the epithelium of human sweat glands. Inulin was not excreted in the sweat. The ratios of the concentrations in sweat to the concentrations in plasma, S/P, of sulfanilamide, sulfapyridine, sulfathiazole, sulfadiazine, and para-aminohippurate were found to be 0.69, 0.58, 0.13, 0.11, and 0.02...