What is the cause of a sour taste in the mouth?

Gastroesophageal reflux disease, or GERD, often leaves a sour or bitter taste in the mouth, according to WebMD. The taste results from the backflow of stomach juices and acid into the esophagus. Persistent heartburn, characterized by a burning pain or uncomfortable feeling behind the breastbone, is another GERD symptom.

Other symptoms of the condition include dull chest pain that feels heavy and uncomfortable as it spreads across the chest, notes WebMD. Some GERD sufferers mistake this pain for the pain that occurs with a heart attack. Trouble swallowing, cough, excess salivation, nausea and hoarseness are additional symptoms that often accompany the sour taste caused by GERD.