The Zynterians are a sentient alien civilization that are native to the galaxy's Alpha or Beta Quadrants. Humanoids by nature, the biochemistry and genetic makeup of Zynterians was extremely similar to that of Xenexians.
The Zynterians invented a form of technology to generate a sensor-dampening Zynterian camouflage screen around an individual's lifesigns. The design of the field works specifically on Zynterians, in other races it will cause discomfort and injury, and likely death. (TNG - Double Helix novel: Double or Nothing)