378 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS e 60 o 30 One week of treatment Two weeks of treatment Figure 10. Change in hand skin condition after one and two weeks treatment with either a 15% glycerol- containing oil-in-water lotion (U1/I) or its base lotion without glycerol (O/O) (p 0.01 after one week and p 0.00 ! after two weeks, Chi-squared test). Percentage of subjects improved is shown above the horizontal axis, and percentage of subjects worse is shown below the horizontal axis (n = 15). 0.01, Chi-squared test), with a further improvement after two weeks (p 0.001 Chi-squared test). The photographs were taken 10 to 12 hours after the last treatment so that no oily product residues remained on the skin surface to mask dryness, thereby also confirming the persistent effects of glycerol in improving the condition of the skin. Figures 1 la and 1 lb clearly illustrate the beneficial effects of such long-term glycerol treatment. DISCUSSION Any effective skin-hydrating product or ingredient must aim at least to maintain the beneficial effects of water on the skin and preferably to enhance and prolong its activity. The results reported here show that treatment with water produced a rapid but short- lived response in all the instrumental techniques used, whereas application of glycerol- containing solutions and products increased and extended the observed effects. In those experiments where a base cream was included, there was an initial peak in instrumental

GLYCEROL TREATMENT OF SKIN 379 ./ Figure 1 la. Hand skin condition before treatment. Figure 1 lb. Hand skin condition of the same subject as shown in Figure 1 la after two weeks use of an oil-in-water lotion containing 15% glycerol.