Infrared Spectroscopic Analysis Indicates That Cocamidopropyl Betaine Has Little Effect on the Stratum Corneum

Cocamidopropyl betaine (CAPB) is an amphoteric surfactant that is commonly used in skin care materials. Although there are many reports about the safety of CAPB, there is limited data about its physical effects on the stratum corneum. Porcine stratum corneum sheets were soaked in 5% or 10% CAPB solution (pH 4.0, 7.0 or 9.0) for up to 60 min at room temperature. After rinsing with distilled water, the properties of the porcine stratum corneum sheets were analyzed using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Sixty min of treatment with 5% CAPB or 10 min of treatment with 10% CAPB did not induce any peak shift at any pH. However, 60 min of treatment with 10% CAPB induced peak shifts of CH2 asymmetric stretching vibration and NH stretching vibration to higher wavenumber values. Although all pH solutions induced those peak shifts, the higher pH solutions caused larger peak shifts. However, 24 hrs treatment with 10% CAPB did not cause swelling at any pH. These results indicate that a long time and/or higher dose of CAPB affects the surface of stratum corneum, but this effect may not be caused by the regular use of CAPB in skin care materials.