150 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS In order to clarify the relationship between tightness and skin gloss, we measured the gloss intensity with a gloss meter, simultaneously comparing gloss with the degree of tightness induced by several surfactants (Figure 2). There is a correlation between {] //' I i i 0 I 2 • '• • Increased Amount of Skin Gloss Figure 2. The relationship between the intensity of skin tightness and increased amount of skin surface gloss. tightness and the occurrence of gloss, with a correlation coefficient of 0.61 (P 0.01), suggesting that tightness is to some extent related to the smoothness of the skin surface. Most anionic surfactants produce the tightness of facial skin approximately 1-5 minutes after washing, but close examination reveals a large difference in the relative intensity of tightness caused by five different surfactants, the order being: SLS ES-2 AGS = SOAP MAP, with significant differences at the 5% probability level by Scheff6's paired comparison method (Figure 3). PHYSICOCHEMICAL ACTIONS OF SURFACTANTS ON SKIN Table II shows the amounts of total amino acids and urocanic acid which are released from the forearm skin after washing for 10 minutes with various surfactants. SOAP and SLS most strongly release total amino acids and urocanic acid, while MAP, ES and AGS produce less of an effect. Furthermore, the release of total amino acids parallels that of urocanic acid, providing a correlation coefficient of 0.98 (P 0.01). In order

SURFACTANT INDUCED SKIN TIGHTNESS 15 ! +0.4 +0.2 -0.2 • - 0.4 MAP SOAP AGS ES SLS Figure 3. Relative intensities of skin tightness induced by five anionic surfactants as shown by the value of the main effect, based on Scheff6's paired comparison method. The tendency for a strong tightness represents a plus sign, and the tendency for a weak tightness, a minus sign. Surfactants having overlapping blocks are not reliably different at the 95% probability level. Table II The Total Amounts of Amino Acids and Urocanic Acid Released From Forearm Skin Following Cup- Shaking Method for l0 Minutes With Various Surfactants at 5% Concentration Total Amino Acids Urocanic Acid Surfactants (nmol/cm 2, n = 4) (nmol/cm 2, n = 8) WATER 40.0 _+ 20.6 • 3.3 -+ 1.0 • MAP 83.8 -+ 23.8 6.2 -+ 2.5 SOAP 163.8 -+ 39.4 13.7 -+ 3.1 AGS 68.1 -+ 31.3 5.0 -+ 2.3 ES 76.3 -+ 53.8 6.2 _+ 2.2 SLS 143.8 -+ 31.3 11.8 -+ 3.6 Mean and standard deviation.