Diethanolamine Esterquats for Hair and Skin and Other Topics: Literature Findings

By: Charles Fox, Independent Consultant

Posted: May 4, 2009, from the May 2009 issue of Cosmetics & Toiletries.

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The following aqueous solutions were tested in contact with pig full-thickness skin (p-FTS): a harsh surfactant solution of 1% sodium dodecyl sulfate (SDS); a harsh surfactant/humectant solution of 1% SDS and 10% glycerol; a mild surfactant solution of 1% sodium cocoyl isethionate (SCI); a control solution of phosphate-buffered saline (PBS); and a humectant solution of 10% glycerol. Sulforhodamine B (SRB), a hydrophilic fluorescent probe, was used to visualize the effects of the five aqueous contacting solutions on the skin barrier morphology.

The results of the TPM visualization study revealed that SDS induces corneocyte damage by denaturing keratins and creating intracorneocyte penetration pathways. On the other hand, SDS and glycerol did not significantly induce corneocyte damage. The dual-channel TPM images corresponding to the mild surfactant solution, the control solution and the humectant solution showed low SRB penetration into the corneocytes as well as localization of the SRB probe within the lipid bilayers surrounding the corneocytes of the stratum corneum (SC).

Through quantification of the amount of SRB penetrating the skin as a function of depth, the researchers found that adding glycerol to an SDS aqueous contacting solution could significantly reduce the SDS-induced penetration depth of SRB, providing evidence of the ability of glycerol to mitigate SDS-induced skin barrier perturbation.

The distribution of SRB in the p-FTS samples was analyzed using a theoretical model that quantified changes in the skin aqueous pore characteristics induced by the four aqueous contacting solutions relative to the control solution. The results of the theoretical model indicate the following ranking order in regard to the extent of perturbation to the skin pores, from highest to lowest: harsh surfactant solution > harsh surfactant/humectants > mild surfactant solution > control solution > humectants solution. The development of such an in vitro visual ranking methodology, including quantification using TPM, could potentially reduce costly in vivo screening procedures, thereby significantly reducing the cost and time-to-market of cosmetic formulations containing surfactants and humectants.

Hair and Hair Care
Hair styling gels: Cosmax Co., Ltd. disclosed hair styling gels containing hair-setting polymers and thickeners.⁴ The described hair styling gel composition comprises: 0.1–10.0% acrylate-polyoxyethylene alkylethyl methacrylate copolymer, 0.1–10.0% acrylate copolymer, 0.1–10.0% acrylate-hydroxy ester acrylate copolymer as the setting polymer, and 0.01–10.0% of a neutralizer, possibly an alkali such as triethanolamine or sodium hydroxide. Acrylate-polyoxyethylene alkylethyl methacrylate copolymer contains 0.1–60.0% hydrophobic monomer as a thickener. The disclosed low viscosity hair styling gel composition is reported to provide high hair fixing ability.