Gastroesophageal Reflux Disease (GERD) is the excessive flow of stomach acid into the esophagus which can damage the esophagus and other parts of the body. Severe and/or frequent heartburn is the main symptom of GERD. GERD can create harmful complications in the body if left untreated.

The esophagus is used for swallowing and GERD sufferers experience heartburn as the main symptom, often right after a meal. Food aggravates GERD, but not necessarily spicy food, although spicy food can make GERD symptoms worse in some patients. Food fills up the stomach and the stomach produces more stomach acid. The esophageal sphincter, which is gate-like and located at the lower section of the esophagus, is supposed to remain closed and only open when liquids or foods are being swallowed. However, in many GERD patients, the esophageal sphincter is "relaxing" more than it should and is letting in excess stomach acid.

Stomach acid easily escapes from the relaxed esophageal sphincter; this escaping or flowing is called "refluxing." Heartburn occurs when the stomach acid creates a burning sensation. Some people with GERD also experience coughing, wheezing, or asthma due to stomach acid connecting with the lungs. Inflammation of the vocal chords resulting in hoarseness can also be a symptom of GERD. Stomach acid is very strong and can erode tooth enamel as some GERD sufferers experience reflux of stomach acid into the mouth.

The United States Department of Health and Human Services estimates that seven million Americans have GERD. Anyone can get GERD, but it is most common in those between forty and sixty-four years of age. Almost everyone will or has experienced heartburn, but not all heartburn is related to GERD. The term GERD has been used for twenty years, but still is not commonly known even by some doctors.

Hiatus hernia is sometimes confused with GERD, but is not the same thing. A hiatus hernia is a dislocated stomach. GERD patients may also have a hiatus hernia if they have complications from GERD such as erosive esophagitis. Erosive esophagitis is a broken esophageal lining. Other complications of GERD include esophageal stricture, or narrowing of the esophagus, and esophageal ulcer.