314 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RESULTS The epicutaneous patch test confirmed in principle earlier findings (1) (Table I). The classical soaps applied at the skin surface in high concentrations and amounts per unit area provoke higher visually estimated scores of damage than the surfactant-type soap. Table II shows the average values of skin surface pH. It is apparent that even 24 hours after application of the test solutions, the three classical soaps enforce an alkaline pH value in contrast to the surfactant-type soap. But after extended use of classical soap for five minutes, the skin surface pH of healthy volunteers returns to weakly acid values two hours later (4) (Figure 1). This result agrees very well with the steep increase of adsorbed Rhodamine B immedi- ately after regular use of the soaps, the relatively quick decay of the anionic pH-depen- Table I Irritancy Potential of 8% and 2% Solutions of Soaps Determined With Finn Chambers (N = 20) Irritancy Score* Concentration D A B C Control 8% • 0.69 0.32 0.55 0.44 0.00 s x 0. 307 0. 249 0. 339 0. 332 0.000 2% • 0.36 0.15 0.35 0.35 0.00 Sx 0.248 0.117 0.232 0.198 0.000 * 0 = no reaction, 0.5 = weak erythema, 1 = strong erythema, and 1.5 = strong erythema, blisters and fissures. Statistical Evaluation of Data (Student t-test) t Values Concentration Comparison DF = 36 8% 2% D/A 4. O64 D/B 1.354 D/C 2.383 D/A 3.347 D/B 0. 135 D/C 0. 144 Thr•s3olds of signi•5'cance.' DF = 35 t Value 95% 99% 99.9% 2.030 2.724 3.591 i & average value. Sx & standard deviation. N /x No. of volunteers. DF & degrees of freedom.

CLEANSING BAR EVALUATION 315 Table II pH values of Skin Sites 24 Hours After Removal of Finn Chambers Containing Soap Solutions Which Were in Place for 24 Hours (N -- 20) Concentration D A B C Control 8% • 7.93 6.53 7.94 7.98 6.24 Sx 0.419 0.453 0.490 0.434 0.607 2% • 7.63 6.37 7.75 7.75 6.16 sx 0.472 0.420 0.473 0. 354 0.615 Statistical Evaluation of Data Student t-test t values Comparison 2% solution 8% solution D/A 11.555 10.404 D/B 1.040 0.038 D/C 1.156 0. 363 D/Control 8.884 10.298 A/Control 1. 179 1.749 Thresholds of signijqcance: DF = 20 t Value 90% 1.729 95% 2.093 99% 2.861 99.9% 3.883 dent surface charge density at the sites treated with classical soaps, and the slow de- crease from a higher level at the sites treated with A (Figure 2). The irritancies of the petrolatum suspensions of free fatty acids from the classical soaps are practically zero in contrast to those of the suspension and solution of A in petro- latum and water respectively (Table III). The relative changes of skin surface fluorescence increase (absolute values) with an in- creasing degree of cutaneous damage (Figures 3, 4). The lowest changes were found at skin sites treated with A or D (Table IV), considering the emission at 450 nm. Consid- ering emission in the 350 nm range, the products listed in order of declining differences between treatment and control are A B D • C (2%, Table V). The investigation of the cleansing efficacy of the soaps confirmed our empirical finding that classical soaps normally have more cleansing power than surfactant-type soap bars (Table VI). To estimate the pH shifts within skin occluded for 24 hours with soap solutions, the pH values of the skin surface were measured after stripping (two male volunteers). An alkaline pH value was found almost down to the glistening layer enabling sodium palmirate/stearate to act as a surfactant. In contrast, the pH value of the skin after