What happens if I don't treat acid reflux?

Mucosal changes. In the worst case scenario, longstanding untreated esophageal reflux can lead to changes in the lining of the esophagus that may increase risk of certain esophageal cancers. You should see your doctor to discuss whether or not your pattern of reflux puts you at higher risk.
Not good. The acid contnues to cause damage to the esophagus. Ultimately can lead to cancer of the esophagus.