Heartburn. Illustration of a raft of foaming ant- acid on top of the contents of a human stomach, taken to stop heartburn. Heartburn is caused by a backflow of the stomach's acidic contents into the oesophagus (upper centre), causing inflammation and a sense of pain that can rise to the throat. It can be brought on by over- eating or by eating too much rich or spicy food. Antacid provides a simple cure by neutralising the acid. Heartburn is one cause of indigestion (dyspepsia).