Some cosmetics and drugs have a formulation of an oil-in-water or a water-in-oil emulsion mainly composed of a water phase and an oil phase component such as milky lotion, cream or ointment.
Conventionally, a surfactant is required in order to manufacture such an oil-in-water or water-in-oil emulsion.
However, a surfactant used in conventional cosmetic treatment often causes skin irritation, so not a few consumers feel misgivings. In addition, an oil-in-water or water-in-oil emulsion containing a surfactant is often criticized as being unstable with passage of time, sticky, and poor in water resistance.
Under these circumstances, several emulsions containing little or no surfactant have recently been developed.
For example, instead of using a surfactant, it is known the emulsion which uses clay mineral (Japanese Unexamined Patent Publication No.56-150007, No.57-16812, No.58-124535 and Japanese Patent Publication No.64-3529), silicone oil (Japanese Unexamined Patent Publication No.61-66752), glycyrrhizin Japanese Unexamined Patent Publication No57-62214), and the like as emulsifier or assistant emulsifier.
Nevertheless, the emulsions shown above do not appear to have improved the stability of the emulsions with passage of time, and, it is too early to speculate at this time that the emulsions shown above have solved the problems relating to skin irritation, stickiness and water resistance.