An epidural steroid is an injection of a local anesthetic and steroid into the epidural space. Due to disc herniation, lots of chemical inflammatory substances are released in the epidural space and the goal is to provide pain relief by reducing the inflammation (swelling) of the nerve roots as they exit the spine. Once the skin is anesthetized with local anesthesia then you will feel a tight sensation when the medicine is being injected. Many patients are done under sedation so the procedure is mostly painless.