Gastroesophageal reflux disease is the medical term for what we know as acid reflux. Acid reflux occurs when the stomach releases its liquid back into the esophagus, causing inflammation and damage to the esophageal lining. The regurgitated acid most often consists of a few compounds: acid, bile, and pepsin. Stomach acid is used in the digestion of food and can be a major irritant to the esophagus due to its tendency to damage tissues. Bile is created in the liver and may back up into the stomach, causing it to be released. Pepsin, the last common compound, is actually an enzyme which helps to kick-start the stomach into breaking down proteins.