Abstract
The relation between skin moisturizing effect and the physical properties of emulsions containing partially hydrogenated yolk phospholipids (HYPL) as the sole emulsifier was examined. The studies revealed the following;
1) The specific characteristic of O/W emulsion containing HYPL as the sole hydrophilic emulsifier was that it formed a thin water undispersible film on the skin after a part of the water had evaporated. This emulsion film has a good affinity with the skin and effectively moisturizes it.
2) The phase transition temperature measured by the micro-viscometry method and the skin surface conductance value of emulsions in HYPL-Squalane-Water system showed a negative linear relation (r=-0.749, p<0.05). This suggests that the phase transition temperature could be one of the physical parameters which influenced the moisturizing ability of skin emulsified with HYPL.
3) In the emulsions containing up to 20% glycerin, a high correlation was found between the skin surface conductance and the water activity (r=-0.932 and -0.958 at 60 and 120 minutes after application, respectively).
This suggests that the water activity is a useful physical parameter for predicting the moisturizing effectiveness of skin treatments in vivo.
