A transudate extraction device (1) for non-invasive extraction of transudate through a target area of a skin barrier of an organism subjected to sufficient ultrasonic energy from a generator (2) to induce transudation therethrough, the device including at least: a contacting means (3) for contacting said target area to receive transudate therefrom, a transudate collection chamber (6) in open communication with said contacting means to receive transudate therefrom, circulating means for circulating transudate within said collection chamber by, for example having a fluid flow (12) through an inlet port (8) and out an outlet port (9) to thereby create and maintain a concentration gradient through the skin of a said test subject, said collection chamber having a discharge opening (9) through which exudate collected therein can be discharged.