One aspect of the invention provides a method for alleviating acne including: applying a therapeutic substance to an area of skin having follicles, said therapeutic substance comprising a plurality of metal nanoparticles within a carrier; using a device to impart mechanical energy to deliver some of said therapeutic substance into a plurality of follicles; removing the composition remaining on the skin surface while leaving the therapeutic substance in said follicles; and irradiating the skin to which the composition was applied with light energy effective to treat acne.