ERYTHEMA QUANTITATION BY SKIN REFLECTANCE 477 i Figure 1. Photograph of the Minolta Chroma Meter (compliments of Minolta Corporation, Ramsey, NJ). Note the small size (8" by 3"by 2") and the convenient hand-held flexible probe. green. The "b*" coordinate signifies relative amounts of yellow and blue. Estimates of changes in redness intensity were made from the "a*" scale, but values for the other coordinates are available from the instrument. Table I Comparison of Instrumental and Visual Assessments of Skin Condition *Treatment Erythema Visual Assessment Minolta-Reflectance ( 4_-_ S.D.) Mean Rank _+ S.D. Before After Transepidermal Water Loss Evaporimetry (g/m2hr _+ S.D.) Before After A 4.2 + 1.3 7.5 -+ 1.5 9.8 + 1.8 5.1 + 3.0 11.4 + 2.6 B 2.5 + 1.2 7.8 + 2.5 8.9 -4-_ 1.7 4.8 + 1.2 9.3 -+ 2.3 C 3.7 -+ 1.1 7.0 + 1.4 9.9 -+ 2.1 4.5 + 1.2 13.5 + 2.7 D 2.1 _+ 0.9 7.1 _+ 1.7 8.8 + 1.9 4.4 + 1.0 8.9 + 2.1 E 4.8 + 1.2 7.5 + 1.8 10.1 + 1.9 4.8 _+ 1.7 13.2 -+ 3.4 F 3.8 + 1.2 7.4 + 1.8 9.5 --+ 1.9 4.8 + 1.5 11.2 + 2.8 * Samples tested were 5 % solutions of various soap and detergent bars. For each assessment, values shown are means of 21 individual patch sites for each sample + standard deviation (S. D.). The six visual scores for each subject were ranked as described in the text. For each column of after-treatment values, means for treatments B and D were not statistically different from each other but were significantly different from the other four treatment means. Treatments A, C, E, and F were not significantly different from each other. Statistical analysis was as described in the text.

478 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RESULTS AND DISCUSSION This paper describes the application of a commercially available reflectance meter to quantify erythema produced by soaps and detergents. We have demonstrated there is a highly significant correlation between skin redness measured by the Minolta Chroma Meter and visually assessed erythema (p 0.001). The Chroma Meter yields reproduc- ible, objective, quantitative measurements of erythema that parallel the subjective vi- sual assessments. Pretreatment (control) assessments by three methods showed an average score of 0 (meaning no erythema) for the visual scores, 7.4 - 0.29 for Minolta redness (a*), and 4.7 - 0.25 g/m 2 hr for transepidermal water loss. All sites were statistically equivalent prior to treatment. Results after the 24-hour treatment are shown in Table I. Visual erythema scores for the six sites on each subject were ranked (for the Friedman Test), _ c D Figure 2. Relationship of visual ranks of product erythema and Minolta Chroma Meter redness readings. The correlation was statistically significant p • 0.003. 7 8 9 10 !! Minolta Reading (a*) Line Equation - 1.77X - 13.34 r= 0.97