What is TENS? Transcutaneous Electrical Nerve Stimulation is a safe, non-invasive, drug free method of controlling pain. It reduces pain by sending small electrical impulses through electrodes that are placed on the skin to underlying nerve fibers to modify your pain perception. The electrodes come in many different sizes so the electrical impulses can be in a small area or a larger area. These electrodes are self adhesive and some are pre-gelled for proper use.