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.

152 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS to evaluate lipid removal ability, we have selected squalene and cholesterol as repre- sentatives of lipids derived from the sebaceous gland and the horny layer, respectively (14,15). Table III shows the amounts of squalene and cholesterol released from forearm Table III Squalene and Cholesterol Released From Forearm Skin Following Cup-Shaking Method for 10 Minutes With Various Surfactants Squalene (A) Cholesterol (B) Surfactant (nmol/cm 2, n = 5) (nmol/cm 2, n -- 5) B/A WATER 0.15 --- 0.15 a 0.16 _+ 0.17 1.06 MAP 0.30 -+ 0.10 0.35 --- 0.15 1.17 SOAP 0.31 --- 0.27 0.47 --- 0.25 1.52 AGS 0.51 - 0.25 0.69 -+ 0.38 1.35 ES 0.50 - 0.25 0.84 _+ 0.05 1.68 SLS 0.67 -+ 0.26 0.99 - 0.23 1.48 Mean and standard deviation. skin after cup-shaking with various surfactants. Consistent with the order of skin tightness-inducing ability, amounts of squalene and cholesterol released by surfactants during washing are in the following order: SLS ES AGS SOAP MAP. In analyzing the ratio of cholesterol to squalene, it has been found that MAP has the lowest ratio among five typical anionic surfactants, suggesting that MAP has a mild effect on the cellular components of the horny layer. We have already described a technique for using indigo carmine for in vivo evaluation of the ability of surfactants to adsorb onto skin (10). This technique is based on ,the principle that skin which has anionic surfactant molecules adsorbed to it will not stain with an acidic dye such as indigo carmine. Table IV depicts the adsorptive abilities of Table IV Adsorptive Ability of Various Surfactants Onto Forearm Skin Following Cup-Shaking Method for 10 Minutes Indigo Carmine Surfactant Staining (E, n -- 8) • (A-B)/A X 100 (%) WATER 15.4 -+ 3.0 (A) b 0 15.5 - 3.6] 0 SOAP 13.5 -+ 4.9 12.3 AGS 12.0 - 4.0 (B) 22.1 ES 5.8 MAP -+ 1.4 62.3 SLS 2.7 - 0.9 82.5 a The intensity of the indigo carmine stain on the skin was evaluated by color difference meter and calculated by Hunter's color difference formula (AE). b Mean and standard deviation. the surfactants evaluated by the indigo carmine technique. From these results, it is clear that SLS and ES adsorb to the skin to the greatest extent, followed by AGS and SOAP, and that MAP possesses the least ability to adsorb to skin.