The application relates to a chemical monitoring system comprising a skin patch for detecting an analyte in perspiration and a processor adapted to receive parameter data and to return an output indicative of a presence of an analyte in a subjects body based on the parameter data. The skin patch 100 includes a first layer 105 permeable to perspiration a second layer 110 coupled to the first layer, the second layer being adapted to receive the perspiration wherein a property of the second layer changes upon receiving the analyte an electrical detector coupled to the second layer, adapted to detect parameter data indicative of the property of the second layer and a flexible electronic circuit 140 coupled to the second layer, comprising a readout circuit for reading parameter data from the electronic detector and a transmitter adapted to transmit the parameter data to a processor. The transmission may be through a radio frequency device. The second layer may be functionalized, contain a polymer matrix, get matrix or polymer layer or have a plurality of probes which interact with the analyte.
