The application relates to a chemical monitoring system comp rising 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 subject' s 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 o f 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.
