SKIN CONDITION MEASURED BY SONIC VELOCITY 11 I II ! I i I I ! i I i i i I ' i I ['• •' , • , '1

12 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Analysis of Variance for the Forearm Test Results Model: Elasticity Change and Visual Grade Change Depend Linearly on Treatment, Time, Sub- ject, and Treatment/Time Effects. Observed Variable ANOVA F Values Elastic Modulus at Time X --Pretreat. Elastic Mod. Visual Grade at Time X --Pretreatment Grade Source Variable Treatment 42.57 (.0001) 86.04 (.0001) Subject 15.06 (.0001) 32.05 (.0001) Time 3.01 (.0069) 27.18 (.0001) Time & Treatment .95 (.5623) 2.85 (.0001) Values in parentheses are the probability that the source variable has no effect on the observed variable. An examination of the F ratios and associated null hypothesis probabilities in the table indicates that treatment, time, and subject significantly affect the observations for both the instrumental and visual techniques. Because of their dependence on time and treatment, both evaluation methods may confidently be utilized to study the dynamic evolution of product effects. However, for the visual grading method, the time- treatment interactive term is a significant aspect of the model, whereas it may be rejected as having a significant effect on the calculated elasticity alterations. This result is consistent with the observations that the sonic velocity measures define treatment- to-treatment differences after only five minutes which remain relatively constant throughout the remainder of the observation times, while the visual grades do not discriminate active treatment differences until much later in the study. Treatment- induced velocity changes occur on a more rapid time scale and are more consistent over time than visual treatment differences. These data lead to the following conclusions. The sonic velocity measurement detects differences between product treatments which are consistent over time. These differences occur on a faster time scale than with visual grades. Product treatments which lead to visual improvement relative to untreated controls cause a 15 to 20% decrease in sonic velocity corresponding to a lower bound jSr a decrease in the elastic modulus of 28 % or 1.1 x 107 N/m 2 of the outermost layer of the skin or a softening effect. Sonic velocity may easily be utilized to quantitate the dynamic effects of acute product treatment on the outer layer skin elasticity. 2. CHRONIC HAND AND BODY LOTION (H&BL) CLINICAL STUDY Sonic velocity measures were examined in the context of a large base, long term H&BL clinical study under realistic product usage conditions. Three fully formulated Hand and Body Lotion products, and a thickened water placebo, were distributed to 350 women residing in a region of the country which normally experiences low relative humidity. The test occurred over a 28-day period after an initial one-week low humidity insult period during which the panelists abstained from all skin care product usage. The dorsal regions of each panelist's hands were graded visually by a dermatologist on the 0 to 5 scale, and instrumentally using the sonic technique, after the insult period. The