The term esophagitis refers to the inflammation of the esophagus. The esophagus is a part of the gastrointestinal tract extending from the pharynx down to the stomach. Acute esophagitis is often caused by ingestion of toxic substances, or by reflux of stomach acid backward into the esophagus, causing a chemical burn. Other rare causes do as well exist. If the cause of acute esophagitis continues over a period of time, the condition is called chronic esophagitis.