O/W microemulsion as a vehicle for sunscreens

In recent years, transparent dispersions or diluted milks have been used as sunscreens. These products contain water-soluble sunscreen agents, and quite frequently are washed away from the skin. However, O/W microemulsions are now being prepared as transparent vehicles for sunscreens. They are waterproof, nonsticky, and easily spreadable. The microemulsions are prepared by using pseudoternary diagrams, by combining lipids with surfactant blends and a polar phase. Soya lecithin and decylpolyglucose produce transparent systems with the lowest percentage of surfactants. These microemulsions contain 4-methylbenzilidene camphor or octylmethoxycinnamate as sunscreen agents. Cyclomethicone, menthol, and allantoin give products a good skin feel, and stearyl methicone gives the waterproof effect. These systems show a Newtonian flux. Little permeation of the sunscreens' trough lipophilic and hydrophilic membrane is evidenced.