526 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Effect of Cationic and Nonionic Surfactants on Stratum Corneum Swelling Per cent Standard Surfactant Conditions Swelling Deviation n a Laurylisoquinolinium bromide (Isothan Q-75) Stearyldimethylbenzylammonium chloride (Triton X-400) Polyoxyethylene (23) lauryl ether (Brij 35) Octylphenoxypolyethoxyethanol (Triton X- 100) .05M 3.9 +3.8 4 20 percent 1.6 -+0.7 4 .05 M, pH 4.8 3.4 +3.4 4 0.1 percent 3.1 -+0.9 4 aNumber of measurements. Table IV Effects of Protein Denaturants and Lipid Solvents on Stratum Corneum Swelling Per cent Standard Reagent Type a Swelling Deviation n b 8M urea D 0 -+0.0 4 5 M guanidine-HCl D 4.1 -+ 1.6 4 0.1 M ammonium thioglycollate D 0 -+0.0 4 0.1 M DTT D 0 -+0.0 4 50 per cent LiBr D 0 -+0.0 4 80 per cent dimethylsulfoxide in water L 0 -+0.0 4 80 per cent N-methylpyrrolidone in water L 0 -+0.0 4 Chloroform: methanol (2:1) L 0.6 -+ 1.0 10 ethyl ether L -4.1 -+ 1.5 6 0.3 per cent performic acid, 15øC D 26.3 -+ 12.9 10 •D is a protein denaturant L is a lipid solvent. bNumber of measurements. Table V Effect of Pretreatment on Sodium Lauryl Sulfate-Induced Swelling of Stratum Corneum Per cent Swelling in • Standard Pretreatment • 0.05M NaLS (pH 6) Deviation H20 13.1 -+3.5 97 CHCla :MeO H delipidized 24.3 -+ 6.2 8 DMSO 36.8 -+2.8 4 DTT reduced 14.2 -+0.1 4 DTT-acrylonitrile alkylated 16.0 -+ 6.3 10 DTT-iodoacetate alkylated 23.4 -+ 5.2 8 Performic acid oxidized - 1.7 ½ -+ 3.2 4 •Abbreviations: DMSO-dimethyl sulfoxide DTT-dithiothreitol. •Number of measurements. øPerformic acid oxidation induced a swelling of 26 per cent, which was not reversible in water. No additional swelling occurred upon exposure to NaLS. while readily detectable swelling was generated in 0.01 M sodium lauryl sulfate.) That a hydrophobic chain in the surfactant favors stratum corneum swelling is indicated by a comparison of results obtained for sodium lauryl sulfate and sodium lauryl ether sulfate (1 mol of ethylene oxide). Sodium lauryl ether sulfate with 3 mol of ethylene oxide