I woke up in severe pain in the middle of the night during one of my cleanses. Not so severe that I had to go to the hospital or anything though. I believe that the attack was caused by a stone that was trapped in the bile duct. More Epsom Salts and olive oil helped. This seems to be pretty rare though. To help prevent stuck stones, take gold coin grass tincture for a few weeks to break up stones. Flushing has changed my life and prevented me from having surgery!! It is worth the small, very small risk of some pain. The vast majority of flushes are completely painless.