Superior effect of isostearyl isostearate on improvement in stratum corneum water permeability barrier function as examined by the plastic occlusion stress test.Int J Cosmet Sci. 2010 Aug; 32(4):304-12.IJ
Dry skin is a major dermatological problem and consumer research indicates that although current moisturizers are effective they are not completely meeting consumer expectation. Several technological approaches have been taken but influencing stratum corneum (SC) lipid phase behaviour as a novel water permeability barrier-enhancing and moisturizing mechanism has only been started to be investigated recently. Both the long periodicity SC lipid lamellar phase and the orthorhombic lipid packing state have been proposed to define optimal SC water permeability barrier properties. Several lipophillic moisturizers have been tested for their ability to modify SC lipid lateral packing namely glyceryl monoisostearate (GMIS), isopropyl isostearate (IPIS) and isostearyl isostearate (ISIS) of which IPIS and ISIS are reported to induce the orthorhombic phase. Despite the improvements in the lateral packing of SC lipids, these ingredients have been shown not to improve transepidermal water loss. However, using a novel skin surface water loss method we have observed for the first time significant improvements in SC water permeability barrier function for ISIS compared with IPIS, GMIS and petrolatum. However, using synthetic membranes and measuring water vapour transport rates we showed that the isostearyl esters were not occlusive like petrolatum. As the effects of ISIS were not because of what would be considered as true occlusion, we propose that the differences in the SC water permeability barrier properties from use of ISIS to the other ingredients tested are because of its reported effects on SC lipid phase behaviour. Further studies probably using spectroscopic approaches, however, will be needed to specifically test this hypothesis in vivo.