TENS is a small device that sends electrical signals into your body through electrodes placed on your skin near the area that hurts. It's not clear exactly how it works, but it gives some people relief.
One theory is that it interrupts pain signals in your nerves. Another idea is that it triggers the release of endorphins -- chemicals that are your body's natural painkillers.
A TENS unit in your home may get you through a flare-up. Most people hurt less while the device is on, but after they turn it off, the pain usually comes back.