NON-IONIC TENSIDES 345 METHOD OF MEASUREMENT The horny layer hydration was determined by capacitance measurement using a Corne- ometer CM 820 (Courage & Khazaka, Cologne, Germany). The depth of measurement ranged from 60 i•m to 100 i•m. The method is critically discussed by Blichmann and Serup (8) as well as by Hashimoto-Kumasaka et al. (9), especially in comparison with other methods that register stratum corneum hydration. The measurements were carried out according to the guidelines published by Berardesca (10). The barrier function was detected with the help of transepidermal water loss using a Tewameter TM 210 (Cour- age & Khazaka, Cologne, Germany). The principle of the measurement method and the guidelines for use are described in detail and discussed by Pinnagoda et al. (11). STATISTICAL EVALUATION The measurements were related to the initial value (TO) before the first washing. Because the distribution was not normal, we carried out a distribution-free Wilcoxon signed- rank test for dependent samples. Average, standard deviation, median, and box (first and fourth quartile or 25% and 75% percentile, respectively) are given in Tables I and II. The significance level for differences was set to p 0.05 high significance was assumed for p 0.01. RESULTS The results are presented in Table I and II, and the statistical evaluation of the differ- ences between the measured values in the individual groups are shown in Table III and IV. Figures 1 and 2 illustrate the results. TRANSEPIDERMAL WATER LOSS The spreading bath and the oil bath with the low tenside content produce an occlusive effect. By contrast, the oil bath with the high tenside content and the water bath lead to increased transepidermal water loss and therefore to barrier damage. The difference between the spreading bath and the oil bath with the low tenside content is small. The water bath does not differ definitively from the bath with the high tenside content. STATE OF HYDRATATION OF THE STRATUM CORNEUM A dehydration effect in the form of a decrease in the capacitance values can be found for water alone and for the bath solution with the high tenside content, without any significant difference between these two baths. The best hydration is seen in the group with the spreading bath, with highly significant differences to the water bath, to the oil bath with high tenside content, and to the oil bath with low tenside content. The bath solution with the low tenside content showed a highly significant increase in the moisture content of the stratum corneum relative to high tenside concentration and the application of water alone, although it was less pronounced than with the spreading bath. The solution with the high tenside content differs from water alone, only at the

346 JOURNAL OF COSMETIC SCIENCE Table I TEWL Values (SD) in g/m 2 x h [averages, standard deviations, median values, and boxes (25% and 75 % percentile)] 15 min M SD Median Box Spreading bath -0.92 1.01 -0.5 - 1.7/0.2 Tween 20: 18% -0.44 1.07 -0.5 -0.8/0.0 Tween 20: 47% 0.29 0.93 0.2 -0.6/1.0 Water 0.34 1.80 0.6 0.0/1.2 30 min M SD Median Box Spreading bath -0.63 1.19 -0.6 - 1.3/0.0 Tween 20: 18% -0.55 1.04 -0.6 -1.0/0.2 Tween 20: 47% 0.11 1.14 0.0 -0.4/0.5 Water 0.53 1.37 0.5 0.1/1.5 60 min M SD Median Box Spreading bath -0.91 1.17 -0.7 - 1.7/-0.2 Tween 20: 18% -0.07 1.33 -0.6 - 1.4/0.0 Tween 20: 47% 0.12 0.86 0.0 -0.7/0.7 Water 0.61 1.64 0.5 0.1/1.5 90 min M SD Median Box Spreading bath - 1.15 0.93 - 1.0 - 2.0/- 0.2 Tween 20: 18% -0.79 0.79 -0.6 -1.1/-0.5 Tween 20: 47% -0.15 1.21 0.0 -0.4/0.8 Water 0.31 1.19 0.5 0.1/1.2 120 min M SD Median Box Spreading bath - 1.28 1.16 - 1.1 - 1.7/-0.5 Tween 20: 18% -0.80 1.20 -0.6 -1.3/0.0 Tween 20: 47% -0.30 1.60 0.0 -1.0/0.6 Water 0.09 1.29 0.3 - 1.0/1.1 end of measurement period at a weakly significant level, so that no definite difference between these groups can be assumed. DISCUSSION The present study was performed with the aim of elucidating the influence of different bath oils with two distinct dissolution characteristics (spreading and dispersion bath oil) and different amounts of a non-ionic tenside on the state of hydration of the stratum corneum and transepidermal water loss, and therefore on barrier function and occlusiv- ity. Two questions were in focus: First, the question of the possible dehydrating and barrier-damaging effect of the non-ionic tenside. Second, the influence of the character of the bath oil (spreading vs dispersion oil bath) on these parameters. The dessicating effect of tensides is established, since the basic work of Blank and Shappirio (12). Gabard eta/. (2) as well as M/filler eta/. (3) could demonstrate a decrease