TENS stands for transcutaneous electrical nerve stimulation. It's a treatment to relieve pain. TENS uses electric currents passed through your skin to block pain signals in your nerves. Using electricity for pain relief has been around for a long time. The ancient Romans and Egyptians placed electric fish over the skin to relieve pain. Today, people use TENS treatment to relieve both muscle and nerve pain. It also may ease pain from inflammation. TENS alone may help some people with mild pain. Combining TENS with medication may help others with more severe pain. Doctors and pain management therapists may use TENS in their offices to treat your pain. You can also learn to use TENS at home. It's a safe treatment that's also easy to use. What is a TENS unit? There are two main types of TENS units. The most common is the conventional TENS. The base of this unit is a handheld device called a pulse generator. It puts out pulses of high-frequency electricity. The pulse generator has wires that attach to pads, called electrodes, that go on your skin—directly over or close to the area where you have pain. The other type is an acupuncture-like TENS—or AL-TENS. This, too, has a pulse generator and wires. But the wires attach to thin needles that go into your skin. When a TENS unit is turned on, electric pulses pass from the base through your skin. With a conventional TENS, you should feel a tingling, but not painful, sensation. AL-TENS is also not painful but may cause some muscle twitching. Work with your therapist or doctor to find the best positions for the electrodes or needles and the best setting. You will also need to find out the length of each treatment that's best for you and how often you need the treatment. How Does TENS work? TENS uses electrical stimulation to block the pain sensations nerves carry to the brain. The different types of TENS may work a bit differently. Conventional TENS: May block nerve fibers outside the brain and spinal cord—peripheral nerves—from carrying pain signals to the brain and spinal cord. May make nerve cells less sensitive to pain. It may also decrease the response to pain in the brain. May cause changes in brain chemicals—neurotransmitters—that may lessen pain. AL-TENS: Uses high-intensity electrical energy. This type of energy may stimulate signals from the brain and spinal cord that block pain pathways. May stimulate natural pain relievers in the brain—opioid receptors. Can TENS Work for You? TENS may help people with short-term pain, long-term pain, back pain, and postoperative pain. However, it doesn't work for everyone. The only way to know whether it will work for you is to try it. You may not be a candidate if you're pregnant, have a pacemaker, have epilepsy, or have certain skin diseases. Although you can get a TENS unit without a prescription, your best bet is to talk with your doctor first.