Device for determining the state of a person's skin, having a film piece made of a non-conductive plastic material and/or polymer-bound textile fabric film which adapts to the topography of the skin surface, which is to be applied to at least one location on the skin and is bonded to this, being self-adhesively bondable fixed flat to the skin, in which are embedded, linked to a sensor: a current or voltage supply unit connected to the sensor, a sensor data measurement and processing unit and a communication unit connected to an antenna, - having a recess which is arranged centrally on the communication unit and passes transversely through the film piece, for visual observation of a respective skin location and/or for repeated application of a cosmetic or medicinal preparation from the outside (as) directly onto the skin of the person, - wherein at least one pair of at least two contact electrodes (3; 3'), which are associated with one another, coextensive, and spaced apart from one another, are arranged as sensors on the film piece on the skin side (hs) and can be laid directly on the skin, - which electrodes are connected respectively via lines laid inside the film to a voltage supply unit arranged there, which can be supplied with current or voltage from the outside (as) using NFC technology, and to at least one impedance, resistance or capacitance measuring unit connected electrically to the voltage supply unit, - from which a passive communication unit can be supplied with the resistance and/or capacitance measurement data by an antenna loop originating from the communication unit, guided likewise within the film of the flat piece, at least around the recess, and laid along this proximal to the borders of the film piece, - which can be retrieved from outside (as) directly as data about skin moisture and/or skin lesion or wound status, and the changes in these over time, using an NFC-enabled communication device from the group containing mobile phone, smartphone or reader - in that the recess in the film piece has a rectangular or square, circular, hexagonal or octagonal shape, characterised - in that at least two times two or two pairs, i.e. a total of at least four, diametrically opposite and respectively associated electrodes (3; 3') are arranged in the film piece, whose mutually opposite borders (31, 31') or edges are rectilinear and run parallel to one another, and are respectively arranged in the vicinity of two mutually opposite borders (21; 21') of the recess, wherein the electrodes are connected to the impedance, resistance or capacitance measuring unit. - having a recess which is arranged centrally on the communication unit and passes transversely through the film piece, for visual observation of a respective skin location and/or for repeated application of a cosmetic or medicinal preparation from the outside (as) directly onto the skin of the person, - wherein at least one pair of at least two contact electrodes (3; 3'), which are associated with one another, coextensive, and spaced apart from one another, are arranged as sensors on the film piece on the skin side (hs) and can be laid directly on the skin, - which electrodes are connected respectively via lines laid inside the film to a voltage supply unit arranged there, which can be supplied with current or voltage from the outside (as) using NFC technology, and to at least one impedance, resistance or capacitance measuring unit connected electrically to the voltage supply unit, - from which a passive communication unit can be supplied with the resistance and/or capacitance measurement data by an antenna loop originating from the communication unit, guided likewise within the film of the flat piece, at least around the recess, and laid along this proximal to the borders of the film piece, - which can be retrieved from outside (as) directly as data about skin moisture and/or skin lesion or wound status, and the changes in these over time, using an NFC-enabled communication device from the group containing mobile phone, smartphone or reader - in that the recess in the film piece has a rectangular or square, circular, hexagonal or octagonal shape, characterised - in that at least two times two or two pairs, i.e. a total of at least four, diametrically opposite and respectively associated electrodes (3; 3') are arranged in the film piece, whose mutually opposite borders (31, 31') or edges are rectilinear and run parallel to one another, and are respectively arranged in the vicinity of two mutually opposite borders (21; 21') of the recess, wherein the electrodes are connected to the impedance, resistance or capacitance measuring unit.