Oesophagitis. Endoscope view of an inflamed and bleeding oesophagus due to oesophagitis. Oesophagitis is usually caused by acid reflux, in which stomach acids enter the lower oesophagus due to poor functioning of the muscle which closes off the entrance to the stomach. It causes heartburn (chest pain). The condition is made worse by smoking, drinking alcohol and obesity. Treatment is aimed at removing the causes, by changing lifestyle and diet. Antacid drugs, which reduce the acidity of the stomach juices, may also provide relief.