Heartburn is a burning sensation that is felt in the chest behind the breastbone. It is caused by the backflow (reflux) of stomach acid into the esophagus.

Heartburn typically occurs within one hour of eating a meal or two hours of lying down. It can last from a few minutes to several hours.

After eating, the food passes from the mouth to the stomach through the esophagus, which is approximately 10 inches long (depending on one's size). To enter the stomach, food must pass through an opening called the lower esophageal sphincter (LES) that serves as a valve between the esophagus and the stomach. When food reaches the LES, the LES relaxes and allows it to enter the stomach. After food enters the stomach, the LES contracts to prevent food and other stomach contents from backing up into the esophagus.

When the LES is weakened or remains relaxed for too long, contents of the stomach can reflux into the esophagus. The tissue lining the esophagus differs from the stomach lining and is more susceptible to acid.

Heartburn is not usually a serious condition. However, severe and chronic heartburn can indicate that a patient has a more serious condition called gastroesophageal reflux disease (GERD), in which the lining of the esophagus may become damaged due to stomach acid reflux.

Contrary to its name, heartburn has nothing to do with the heart. However, heartburn is sometimes confused with symptoms of a heart attack. Sophisticated medical equipment is sometimes needed to distinguish between the two.

Anybody, even children, can be affected by heartburn. It is particularly common among pregnant women, because pregnancy increases pressure on the stomach and diaphragm. Hormonal changes may also cause the LES to relax.

Heartburn is one of the most common ailments in the United States. More than 60 million adults experience heartburn at least once a month. Some studies have indicated that more than 15 million adults experience heartburn daily, according to the American College of Gastroenterology.