Abstract: Devices and methods of detecting gas and volatile organic compounds from skin are disclosed. One system for detecting emissions through skin includes a sensing device having a housing having a top portion and a bottom portion, the bottom portion having a concave-shaped bottom surface creating a cavity region, the at least one light source arranged to emit a spectral range of wavelengths of light into the cavity region, and at least one sensor disposed to receive light emitted by the at least one sensor after the light propagates through at least a portion of the cavity region, the at least one sensor configured to generate a signal based on the received light. The sensing device may also include a communication module configured wirelessly transmit the spectral information to a mobile device for determining a characteristic, for example, a blood glucose level.