ANTI-IRRITANTS AND TANNING ACCELERATORS 377 study and their findings can be accounted for by the fact that in this study Aa* was compared with visual assessment while a* values on the treated sites were used by Babluk et al. The instrument, because of its sensitivity and accuracy, has been utilized in development of techniques for estimation of efficacy of anti-irritant products. The major chromophore for visible light in the epidermis is melanin. The effect of radiation after 24 hours determines the erythema and is independent of the L* value if immediate pigment darkening is ignored. The stimulation of melanin manifested by tanning response is detected by the reflectance L* values after 48-72 hours, and it does not correlate to skin erythema a* values (Table V). According to the observations of Seitz and Whitmore (1988), yellow coloration (b* values) exhibits a significant correlation with the tanning effect. In our results we ob- served the same however, we believe that yellow measurements alone do not depict the tanning response. A combination of L*, a*, and b* in the form of AE* can be obtained to obtain a complete picture of the tanning effect. Nevertheless, it is the reflectance (L*) values that are the most important to show darkness of skin due to tanning. Visual and instrumental estimation of skin darkness/tanning response revealed a good correlation 0.895 (p 0.001). Comparison of subjective and objective quantification (9) shows that each subjective grading corresponds to a broad range of color values and that there is a slight overlap between consecutive grades. This is understandable, as the subjective grading represents truncation of a continuous range of color values into a limited number of discrete brackets and bears subjective variation that may exist among different clinical personnel or that occurs in the same observers at different times. Objective assessment is better than subjective grading since it extends discrete subjec- tive grading to a continuous range of numbers, thus making possible a meaningful dose response curve. The linear dose response curve between radiation dose and degree of tanning, from our studies, provides a new approach for the calculation of the tanning response and the quantification of the efficacy of tanning products. REFERENCES (1) R. Breit and A.M. Kligman, "Measurement of Erythemal and Pigmentary Responses to Ultraviolet Radiation at Different Spectral Qualities," in The Biological Effects of Ultraviolet Radiation with Emphasis on the Skin, F. Urbach, Ed. (Pergamon Press, Oxford, 1969), p. 267. (2) P. M. Farr and B. L. Diffey, Quantitative studies on cutaneous erythema induced by ultraviolet radiation, Br. J. Dermatol., 111, 673-682 (1984). (3) S. W. Babulak, L. D. Rhein, D. D. Scala, F. A. Simion, and G. L. Grove. Quantitation of ery- thema in a soap chamber test using the Minolta Chroma (reflectance) Meter: Comparison of instru- mental results with visual assessments, J. Soc. Cosmet. Chem., 37, 475-479 (1986). (4) M. Forsbeck and E. Skog, Immediate reactions to patch tests with Balsam of Peru, Contact Dermatitis, 3, 201-205 (1977). (5) J. B. Dawson, D. J. Barker, and D. J. Ellis, A theoretical and experimental study of light absorption and scattering by in vivo skin, Phys. Med. Biol., 25, 695-709 (1980). (6) H. Tronnier, "Evaluation and Measurement of Ultraviolet Erythema," in The Biological Effects of Ultraviolet Radiation With Emphasis on the Skin, F. Urbach, Ed. (Pergamon Press, Oxford, 1969) p. 267. (7) F. Daniels and J. D. Imbrie, Comparison between visual grading and reflectance measurements of erythema produced by sunlight,./. Invest. Dermatol., 30, 295 (1958). (8) S. Wan, K. F. Jaenicke, and J. A. Parrish, Comparison of the erythemogenic effectiveness of ultravi-

378 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS olet-B (290-320 nm) and ultraviolet-A (320-400 nm) radiation by skin reflectance, Photochem. Photot•iol., 37, 537-542 (1983). (9) S. Wan, J. A. Parrish, and K. F. Jaenicke, Quantitative evaluation of ultraviolet induced erythema, Photochem. Photot•iol., 37, 643-648 (1983). (10) P. J. Frosch and A.M. Kligman, The soap chamber test. A new method for assessing the irritation of soaps,J. Am. Acad. Dermatol., 1, 35-41 (1979). (11) L. L. Hantman, Methods for studying the skin surface, J. Soc. Cosmet. Chem., 34, 407-418 (1984). (12) W. Westerhof, B. A. A.M. van Hasselt, and A. Kammeijer, Quantification of UV-induced ery- thema with a portable computer controlled chromameter, Photoderm., 3, 310-314 (1986). (13) B. L. Diffey, R. J. Oliver, and P.M. Farr, A portable instrument for quantifying erythema induced by ultraviolet radiation, Br, J. Dermatol., 111, 663-672 (1984). (14) J. C. Seitz and C. G. Whitmore, Measurement of erythema and tanning responses in human skin using a tri-stimulus colorimeter, Dermatologica, 177, 70-75 (1988).