Tens units have been prescribed for years as an alternative to traditional analgesic pain relievers. How Does a TENS Unit work? Electrodes are placed on or near the area of pain. Soothing pulses are sent via the electrodes through the skin and along the nerve fibers. The pulses (controlled by the user at all times) suppress pain signals to the brain. TENS Machines also encourage the body to produce higher levels of its own natural pain killing chemicals called Endorphins and Encephalins.