ASSESSMENT OF SKIN CARE PRODUCTS 3 N 125- 1 oo 75 50 25 102 117 86 N: 368 mean age = 36,1 years 40 51 - 60 17 16 - 20 21 - 30 31 - 40 41 - 50 60 Age (years) Figure 1. Age distribution. Description of the method. The corneometer CM 420 consists of a plastic casing and a sensor, also referred to as a measuring head. On the display panel of the casing the measured value is represented as a max. three-digit number. The measuring head has a cylindrical shape. The measuring principle requires even positioning of the front face with a constant pressure. By means of a spring, the inner movable part--the active front face•is pressed to the skin with approx. 3.5 N in each case. The mode of operation of the corneometer CM 420 is based on changes in electrical capacitance that are caused by the differences of the water content in the measuring volume. The front face of the measuring head is a flat capacitor in the capacity field (= measuring volume) on which the skin surface is placed. Measurement. For the measurement, the measuring head is pressed onto the skin to be measured (see above). Attention must be paid to the fact that the measuring result can be influenced by the following factors: ß Uneven positioning of the measuring head front face (caused by excessive pressure, extremely slanted position, irregular surface of the segment to be measured, hairs) ß Measurement during or directly after emotional stress or physical strain (e.g., movements) ß Presence of conducting substances on skin ß Measurement in the case of extreme room humidity and/or room temperature ß Longer application of the measuring head (due to occlusion effect) ß Soiling, moistening, or damage of the foil covering the measuring head front face After one week of preparation without cosmetic treatment, two groups of test persons applied product N and/or K twice a day onto the inner side of the forearm (half of the volunteer groups on the left arm, the second half on the right), while the other arm remained untreated for comparison. The measurement was carried out before the treat- ment started, after two weeks, and after four weeks, 12 hours after the last application. Results are shown in Table I. Columns contain the mean corneometer values for product and control side, and an efficacy value that is expressed by the relative difference ratio

4 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS between product and control. Significant improvement in skin moisture after the four- week test period could be assessed at all centers. The highest values were measured at center Be and the lowest at center We. No difference was found between the two test products. Skin roughness Methylene blue method Principle: Skin roughness is assessed via adsorption and desorption of the dyestuff methylene blue. The quantity of the adsorbed dyestuff is proportional to skin roughness (25). Experimental: Test glasses (see below) are fixed with tourniquets. 5 ml of solution 1 is filled through a hole in the bottom of the glass, and the measurement area is washed by moving the arms for 30 seconds. The wash solution is removed following a second rinse with 10 ml of distilled water for 60 seconds. Test glasses are removed, and measurement Table I Skin Parameter: Moisture Method: Corneometer Before treatment After four weeks of daily treatment Product K Product Control Product Control Efficacy N 31 31 33 33 Be mean 73.3 75.2 85.1 71.3 s 6.5 7.5 7.5 7.4 N 34 34 33 33 He mean 67.2 68.3 75.4 69.1 s 5.9 5.8 7.3 6.8 N 30 30 30 30 R mean 66.6 67.6 71.9 67.5 s 6.1 6.6 6.2 5.8 N 40 40 40 40 We mean 73.5 73.5 77.1 72.8 s 5.1 5.1 7.1 6.7 19.4%* 9.1%* 6.5%* 5.9%* Before treatment After four weeks of daily treatment Product N Product Control Product Control Efficacy N 32 32 35 35 Be mean 71.0 73.0 85.3 73.7 s 8.7 8.9 8.8 8.2 N 34 34 34 34 He mean 64.8 65.9 75.2 68.1 s 6.0 6.1 8.8 6.9 N 30 30 30 30 R mean 68.6 67.9 71.9 66.1 s 6.2 5.4 7.1 6.8 N 40 40 40 40 We mean 72.3 72.6 75.7 71.9 s 6.2 5.0 5.8 5.8 15.7%* 10.4%* 8.8%* 5.3%* N = sample size mean = average s = standard deviation. Efficacy: relative product efficacy ratio (product-control) ß 100/control. ß Highly significant efficacy of the product in comparison to the control.