Recently, a novel microsensor to measure the transepidermal water loss (TEWL) of the human skin has been developed. The sensor is based on an interdigital electrode system covered with a highly hygroscopic salt film. It is mounted inside a closed chamber arrangement in a distance of about 1.4 mm away from the skin. In this paper, the authors present a new method to evaluate and calibrate the sensor device. Different TEWL values are imitated by a variable humidity source. Furthermore, the very high sensitivity of the TEWL sensor is demonstrated. The output signal represented by the conductance of the sensor varies over six orders of magnitude in the relevant TEWL range between 2 and 60 g/(m2middoth)