Skin and Skin Care SCI mildness studies: Ghosh et al. have studied the mildness of sodium cocoyl isethionate (SCI) on the skin barrier via an in vitro investigation of the relative sizes of the SCI micelles and skin pores.1 SCI is an important surfactant ingredient in mild, synthetic detergent (syndet) cleansing bars, and studies have shown it is more mild and less damaging to the skin barrier than soaps and surfactants such as sodium dodecyl sulfate (SDS).
Researchers have shown that in aqueous solutions SDS forms smaller micelles than the pores in the stratum corneum (SC), and as a result, the SDS micelles can contribute to SDS skin penetration and induce skin barrier perturbation. In the presented research, the authors attempt to explain the well-documented skin mildness of SCI by examining the size of the SCI micelles relative to that of the aqueous pores in the SC. For this purpose, in vitro mannitol skin permeability and average skin resistance measurements were taken after skin was exposed to an aqueous SCI solution. In this context, the hindrance of solution transported though the pores in the SC was measured.
The studies demonstrated that an SCI micelle radius of 33.5 ± 1 Å, as determined using dynamic light-scattering measurements, showed significant steric hindrance and could not penetrate into the SC through aqueous pores with an average radius of 29 ± 5 Å. The researchers believed that the inability of the SCI micelles to contribute to SCI skin penetration and associated skin barrier perturbation is responsible for the observed skin mildness of SCI.