When stomach acids repeatedly back up into the esophagus, they can injure the esophagus’ sensitive lining. That injury can lead to uncomfortable inflammation called esophagitis. Eventually, the acid wears away at the esophagus, causing bleeding. If the bleeding is heavy enough, blood can pass into the digestive tract and show up as dark, tarry stools. Esophagitis can cause ulcers—sensitive, open sores on the lining of the esophagus. In a small percentage of people, long-term acid exposure from GERD leads to a condition called Barrett's esophagus (BE). In BE, new cells form to take the place of those damaged by acid reflux.