When the stomach acid reflux is short-term, there is generally no damage to the esophageal lining, and this is known as non-erosive GERD (where the tissue is not eroded by the stomach acid). In long-standing cases of GERD where the esophageal lining is repeatedly in contact with the stomach acid, the tissue undergoes damage, and this is known as erosive GERD (where the tissue is eroded by the stomach acid). In short, if non-erosive GERD is prolonged and untreated, it can turn into erosive GERD.