GERD is caused by frequent acid reflux â€” the backup of stomach acid or bile into the esophagus.
When you swallow, the lower esophageal sphincter â€” a circular band of muscle around the bottom part of your esophagus â€” relaxes to allow food and liquid to flow down into your stomach. Then it closes again.
However, if this valve relaxes abnormally or weakens, stomach acid can flow back up into your esophagus, causing frequent heartburn and disrupting your daily life. This constant backwash of acid can irritate the lining of your esophagus, causing it to become inflamed (esophagitis). Over time, the inflammation can erode the esophagus, causing complications such as bleeding or breathing problems.