Described herein are transdermal solvent systems comprising at least one active agent in solution in a base solution, the base solution comprising at least one fatty acid ester compound, at least one monoterpene compound and a co-solvent in the form of DMSO or DMI and at least one plant oil. The base solution was found to be highly versatile and provide superior or at least comparable skin penetration efficacy and active agent compatibility. Methods of treatment, uses of the solvent system and methods of manufacture are also described.