A colloidal anionic oil-in-water emulsion includes a prostaglandin, an oil having a iodine value ≦2, a surfactant and water, provided the anionic oil-in-water emulsion does not contain polyvinyl alcohol. The use of the anionic oil-in-water emulsions for enhancing the stability of the prostaglandins, for the treatment of ocular hypertension and/or glaucoma, for promoting growth of eyelashes and/or for treating eyelash hypotrichosis is also described.
