Gastroesophageal Reflux Disease, or GERD, occurs when the lower esophageal sphincter (LES) does not close properly, and stomach contents splash back, or reflux, into the esophagus. The LES is a ring of muscle at the bottom of the esophagus that acts like a camera shutter between the esophagus and the stomach. The esophagus carries food from the mouth to the stomach.

When reflux stomach acid touches the lining of the esophagus, it causes a burning sensation in the chest or throat called heartburn. The fluid may even be tasted in the back of the mouth, and this is called acid indigestion. Occasional heartburn is common but does not necessarily mean one has GERD. Heartburn that occurs more than twice a week may be considered GERD, which can eventually lead to more serious health problems.