An oil based composition for external use on skin for enhancing percutaneous absorption of a water-soluble agent contains 50% by mass to 95% by mass of an oil constituent, which contains 10% by mass to 100% by mass of a solid or semisolid oil constituent, and 5% by mass to 50% by mass of particles. The composition has occlusivity of at least 50% and is adapted for use such that, after a preparation for external use on skin, which preparation contains a water-soluble agent, has been applied onto skin, the composition may be applied onto the preparation for external use on skin, which preparation has been applied onto the skin. A method of enhancing percutaneous absorption of a water-soluble agent utilizes the composition.