A sweat sensor device (200) includes one or more sweat sensors (220) and a seal (280) covering the one or more sweat sensors (220). The seal (280) is adapted to protect the sweat sensors (220) from outside contaminants when the device (200) is placed on the skin (12). The sweat sensor device (200) may include an absorbing medium (230) to absorb sweat from the skin (12) that is covered by the seal (280). The seal (280) can be permeable to gas, permeable to water and impermeable to at least one aqueous solute, or selectively permeable to at least one aqueous solute. The sweat sensor device (200) may include an artificial sweat stimulation mechanism (345) for stimulating sweat when the device (200) is placed on the skin (12).