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Advantage of Sodium Polyoxyethylene Lauryl Ether Carboxylate as a Mild Cleansing Agent. Part 2: Effects on Skin Functions and Conditions
Author(s) -
Endo Koji,
Ozawa Toshiaki,
Masui Takashi,
Ichihashi Toshiki,
Yanagawa Kiyotaka,
Miyaki Masahiro,
Matsuo Keiko,
Yamada Shinji
Publication year - 2018
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1002/jsde.12177
Subject(s) - chemistry , pulmonary surfactant , stratum corneum , penetration (warfare) , carboxylate , chromatography , stereochemistry , medicine , biochemistry , pathology , operations research , engineering
The relationship between skin stratum corneum (SC) swelling induced by the treatment of surfactant solutions and skin functions/conditions was investigated in vivo for six anionic surfactants used in commercial skin cleansers. A skin soak test was carried out (2% heavy water [D 2 O] solutions) on the inner surface of forearm skin; the D 2 O depth profile in the SC was obtained using confocal Raman spectroscopy to evaluate the solution penetration. The D 2 O depth profile had a plateau layer near the skin surface and the water content decreased progressively with depth. This profile indicates the presence of a diffusion front of the penetrated surfactants at the boundary of the two layers; the surfactant concentration is higher in the inner side of the front (plateau layer near the skin surface) than the deeper section. After continual treatments with the solutions for 3 days, the SC hydration, water permeability, and the degree of skin irritation were all found to be related to the plateau layer thickness of D 2 O; small thickness gave little reduction of SC functions/conditions. When the plateau thickness is small, the damaged section in the SC could be renewed by turnover, and little accumulation of the damage during cleansing may be expected with repeated use. In our study, sodium polyoxyethylene lauryl ether carboxylate (EC) had the thinnest plateau layer and exhibited smallest changes in the skin functions/conditions. For practical purposes, the formulation of a mild skin cleanser is obtained by replacing part of the main surfactant base with EC.