288 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) A. J. Quattrone and K. Laden, Physical techniques for assessing skin moisturization, J. Sac. Cosmet. Chem., 27, 607-623 (1976). O. R. Potts, Stratum corneum hydration: Experimental techniques and interpretation of results, J. Sac. Cosmet. Chem., 37, 9-33 (1986). R. L. Anderson, J. M. Cassidy, J. R. Hansen, and W. Yellin, Hydration of stratum corneum, Biapalymers, 12, 2789-2802 (1973). E. F. E. Cooper and B. F. Van Duzee, Diffusion theory analysis of transepidermal water loss through occlusive films, J. Sac. Cosmet. Chem., 27, 555-558 (1976). O. K. F. Jacobi, Nature of cosmetic films on the skin, J. Sac. Cosmet. Chem., 18, 149-160 (1967). R. L. G. Rietschel, A skin moisturization assay, J. Sac. Cosmet. Chem., 30, 369-373 (1979). M. M. H. Rieger and D. E. Deem, Skin moisturizers. II. The effects of cosmetic ingredients on human stratum corneum, J. Soc. Cosmet. Chem., 25, 253-262 (1974). L. M. Lieb, R. A. Nash, J. R. Matias, and N. Orentreich, A new in vitro method for transepidermal water loss: A possible method for moisturizer evaluation, J. Sac. Cosmet. Chem., 39, 107-119 (1988). M. Loden and M. Lindberg, The influence of a single application of different moisturizers on the skin capacitance, Acta. Derm. Venereal. (Stackh.), 71, 79-82 (1991). A. Frithz, Investigation of cortesal, a hydrocortisone cream and its water-retaining cream base in the treatment of xerotic skin and dry eczemas, Curr. Ther. Res., 33, 930-935 (1983).

J. Soc. Cosmet. Chem., 44, 289-297 (September/October 1993) The methylene blue and image analysis tests for determining skin roughness: A critical assessment based on data in the literature F.-J. WORTMANN and G. WORTMANN, Deutsches Wollforschungsinstitut, Veltmanplatz 8, D-51 Aachen, Germany. Received November 9, 1992. Synopsis The correlation of data published by Schrader et al. (2) for skin roughness measurements using the methylene blue and image analysis methods is investigated. The results show that the correlation between the methods is poor and unsatisfactory for prediction and calibration purposes. A classification of the data into four classes shows a pronounced inconsistency between results of the two methods. This in turn leads to serious questions, if not doubts, with respect to the validity, reproducibility, and accuracy of the tests when specifying the performance of skin care products. INTRODUCTION On page 980 of his well-known book, Schrader (1) points out (in translation) that Scientific procedures for the evaluation of cosmetic products are continuously gaining importance. To fulfill the high quality standards, demanded nowadays by the market, optimization of products just for optical appearance and for processing performance is insufficient. Testing procedures of practical relevance are required to quantify reproducibly the positive and negative effects of cosmetic products. For skin care products an important effect is related to the reduction of skin roughness. For a recent paper, Schrader and Bielfeldt (2) conducted comparative studies of skin roughness measurements, using image analysis and several in vivo skin testing methods, including the methylene blue adsorption test. According to Schrader (1), the methylene blue test is a simple method for the evaluation of skin roughness. The rougher the skin, the larger its surface and the more intensive the absorption of methylene blue. The methylene blue method has been widely used for industrial quality improvement and control purposes, as well as for reasons of consumer information and protection (3). In their paper, Schrader et al. (2) present, besides other results, a set of data for a range of skin care products, using the methylene blue test as an indirect method and the image analysis method as a direct method for evaluating skin roughness. On investi- 289