JOURNAL OF COSMETIC SCIENCE 80 indicates potentially better longevity of the tan generated by X vs K. In vivo data were also plotted in the respective fi gures below. Figure 6 illustrates “the natural universe of suntan tonality” (9) via the balance between changes in the yellow and red components of the natural suntan. The natural universe of suntan tonality determines how “natural” the tonality of a sunless tan appears relative to a truly natural, sun-generated tan. All mea- surements associated with X were within the “natural universe of suntan tonality” range, providing that the sunless tan generated by X is comparable to a natural sun-induced tan for all panelists (Figure 6). Figure 7 shows the balance between changes in Chroma, ΔC*, and in refl ectance, ΔL*, induced by the test articles in the realm of the “natural universe of suntan” (9) for sun-induced tan. Overall, X produced a sunless tan color consistent with the “natural universe of suntan tonality” range, except for one panelist, whose color was outside the range, but the rest of the panelists had close color responses and were well within the range (Figure 7). Application of K resulted in three panelists being outside the “natural universe of suntan tonality” range (Figure 6). Two of the panelists developed a color that was more yellow than Figure 4. Changes in ΔC* and ΔL* values in vitro at 72 hours. ΔL* values indicate the “darkening” trend. Table IV ITA° Values of Panelists ITA° values* Panelist Left forearm Right forearm Skin color categories 1 52.86 51.71 Light (41 to 55) 2 52.48 55.74 Light (41 to 55) to very light (55) 3 50.47 55.12 Light (41 to 55) to very light (55) 4 53.01 51.75 Light (41 to 55) 5 39.78 40.55 Intermediate (28 to 41) *ITA = [Arc tangent ((L*-50)/b*)] 180/3.1416.

SUNLESS TANNING FORMULATIONS 81 natural suntan, while another panelist seemed to have less red than natural suntan. The tonality of the sunless tan generated by K was less “natural” since three out of fi ve panel- ists were outside the “natural universe of suntan tonality” range. K also produced the following results based on ΔC* and ΔL* measurements: one of the fi ve panelists was out- side the “natural universe of suntan tonality” range and another panelist had a less devel- oped tan that was on the borderline of the range (Figure 7). Figure 5. Impact of the test articles on ΔE*ab values in vivo vs time. Figure 6. Impact on color response in vivo at 24 hours.