You've just eaten a big meal and leaned back in your favorite chair. Then it happens. Your chest starts to hurt so much it feels like it's on fire.

You may also experience a sour taste and the sensation of food re-entering your mouth (regurgitation). It results from gastroesophageal reflux, a condition in which stomach acid or, occasionally, bile salts back up into your food pipe (esophagus). When there's also evidence of esophageal irritation or inflammation, you have gastroesophageal reflux disease (GERD).

Normally, the lower esophageal sphincter blocks most acid from coming up into the esophagus. This circular band of muscle at the lower end of the esophagus doesn't open except when you swallow. If the sphincter relaxes abnormally or weakens, stomach acid can back up and cause heartburn.

Most people can manage the discomfort of heartburn with lifestyle modifications, such as improved diet, over-the-counter antacids and weight loss. But if heartburn is severe, these remedies may offer only temporary or partial relief. You may need newer, more potent medications to reduce symptoms.

Signs and symptoms

If you experience heartburn, you may also experience these signs and symptoms:

• Asthma

• Chest pain

Causes

When you swallow, the lower esophageal sphincter — a circular band of muscle around the bottom part of your esophagus — relaxes to allow food and liquid to flow down into your stomach. When it relaxes at any other time, stomach acid flows back up into your esophagus, even if you're in an upright position. The acid backup is worse when you're bent over or lying down. Some factors that can cause the sphincter to relax abnormally include:

• Asthma

• Chest pain