Three sunscreen compounds, p-amino benzoic acid (PABA), octyl-dimethyl
-p-amino benzoic acid (ODP), and 2-hydroxy-4-methyoxy-5-sulfobenzophen
one (HMSB) were incorporated into a model microemulsion system stabili
zed by sodium dodecyl sulfate and pentanol. The PABA acted as a hydrot
rope supporting the stability of an oil-in-water microemulsion, while
ODP had the opposite effect. HMSB, finally retained both the oil-in-wa
ter and the water-in-oil parts of the microemulsion system.