172 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS large numbers of subjects. They therefore allow an objective characterization of the human stratum corneum and its functional state. In this regard, no area of skin is more complex than the face, and none is more interesting. Genetic and environmental influ- ences have a huge impact on the quality of facial skin. Dry facial skin is a very frequent complaint of middle-aged women, and extraordinary measures are used to combat it. To gain better insight into the nature of dry skin, we made a number of nonintrusive measurements. MATERIAL AND METHODS This investigation was carried out on 55 human volunteers at the Skin Study Center (Philadelphia, PA) in January when dry skin is worst. The subjects were selected for severity of dry skin by screening from a group of 165 people. Informed consent was obtained. Except for a mild soap that was provided, the skin received no cosmetic applications for two weeks prior to the first measurement. DRYNESS SCORING Dryness of the forehead and cheeks was scored by an experienced physician, following the global grading system of Kligman: 0 = surface smooth, no peeling. 1 = slight dryness sparse, small scales. 2 = moderate dryness larger, more numerous scales. 3 = extreme dryness prominent large scales, densely covering the surface. BIOPHYSICAL MEASUREMENTS 1. Extensibility of the stratum corneum was measured on the cheek by means of the Twistometer ©, which applies a weak torque to a disc through a twist of about 3 ø (6). When the distance between the disc and a surrounding guard ring is less than 1 mm, the measurement reflects the resistance of the stratum corneum to stretching, an indi- rect measure of its degree of hydration. 2. Electrical conductance was determined on the cheek and forehead, by means of a DermoDiag © (7). This instrument is an auto-oscillator that delivers 27 MHz waves. The coaxial cylindrical electrode is applied under a constant pressure for a constant time. 3. Forced desquamation of corneocytes was carried out by a turbine machine which mechanically rotates a disc of wool in a glass cup filled with a Triton X 100 solution as in the detergent scrub technique (8). 4. Transepidermal water loss (TEWL) was determined on the forehead using the Ser- vomed © evaporimeter after the method of Nilson (3). The subjects were at rest for at least 45 minutes till steady-state values were obtained. ß 5. Sebum excretion rate (SER) was measured on the forehead using the lipometre © as previously described (4). The forehead was cleaned by wiping with cotton balls soaked

DRY FACIAL SKIN 173 in ethanol:water (70/30). One hour later, the site was sampled four times in succession and sebum excretion expressed as •g/cm2/min (5). STATISTICS Statistical analysis employed SAS (North Carolina), using a VAX 750 computer. Corre- lations among parameters were determined according to Kendall/Spearman procedures. Correlation coefficients (r) and statistical significance (p) have been calculated for all the experimental data. RESULTS The distribution of the dryness scores, on cheek and forehead, for the subjects in this investigation is summarized in Figure 1. For simplicity, we have divided the popula- tion into three groups, viz 1, 1 - 2 , 2 where 1, is marginal dryness. It is noteworthy that 70% of the subjects had appreciable dryness on the cheeks, while the figure for the forehead was only 10%. SC EXTENSIBILITY Figure 2 reveals a striking decrease in SC extensibility as the dryness score increases (r = -0.55, p 0.001). 40- CHEEK FOREHERD o r• m,m '-! Z 30 10 1 (1-2) DRYNESS SCORE