20 MHz B-SCANNING 247 Figure 2. Image representing the echographic aspect of normal skin of the volar forearm. It is characterized by two hyper-reflecting areas, the first, represented by the entry echo, corresponding to the epidermis, and the second in the lower dermis. cation of an oil-in-water emulsion by performing instrumental measurements for up to 360 minutes (7). They observed an immediate rise in TEWL values, which in 15 minutes returned to the original level, and a slight increase in hydration values, as measured by capacitance and conductance, which persisted throughout the whole study. According to these results, they supposed that the biophysical changes in the skin following a single application of an oil-in-water emulsion can be divided into two distinct phases, an initial evaporation phase, which lasts less than 15 minutes, dominated by evaporation of emulsion water and increased hydration, and a lipidization phase lasting for at least 360 minutes and dominated by the oil phase of the emulsion, associated with minor improvements of hydration parameters (7). These observations were confirmed by Lod•n, who hypothesized that emollients can increase the water content of the stratum

248 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 3. Image representing the echographic aspect of the skin of the volar forearm after application of petrolatum. The epidermis echo and the echogenicity of the lower dermis have clearly decreased in com- parison to normal skin. Table III Superficial 201-255 Pixels at Skin Sites Treated With Petrolatum and Two Commercial Products Petrolatum Moisturizer 1 Moisturizer 2 Baseline 352.73 + 223.92 368.33 + 227.48 428.4 + 183.74 Removal 183.87' + 67.78 167.33' _+ 62.23 191.13' _+ 82.56 15 min 252.47* + 103.86 181.73' _+ 62.81 222.8* + 95.76 30 min 220.67* _+ 75.52 168.33' + 49.85 231.2' + 93.5 60 min 221.33' + 74.72 206.53* + 102.02 258.4* + 113.82 120 min 201.8' + 86.25 208.53* _+ 106.19 232.33* _+ 99.83 180 min 207.47* _+ 80.91 217.73' + 72.6 267.13' + 88.06 * Significant in respect to baseline.