A waveguide couples an acoustic source (such as an ultrasound transducer) to a cosmetic product (such as a liquid or gel-based skin care product) applied to the skin. In one representative embodiment, a distal surface of the waveguide is placed in contact with a relatively thin layer of skin care product that has been applied to the skin. Alternatively, the thin layer can be applied to the distal face of the waveguide, and then the waveguide placed on the skin. The cosmetic product may be formulated such that when ultrasound energy is directed into the cosmetic product via the waveguide, microspheres in the cosmetic product oscillate and increase the permeability of the skin to active beneficial agents included in the cosmetic product.
