Provided are an ultrasound system and methods that deliver medication through skin by using multiple frequencies. The method to deliver medication through skin include irradiating the skin with ultrasound having a first frequency to cavitate a skin tissue irradiating the skin with ultrasound having a second frequency, which is lower than the first frequency, to collapse the cavitated tissue and delivering the medication through the collapsed tissue, wherein a single transducer is configured to produce the ultrasound having the first frequency and the ultrasound having the second frequency.
