Gastroesophageal reflux disease (GERD), commonly known as reflux, occurs when stomach acid repeatedly flows back into the esophagus. This happens due to prolonged and excessive exposure of the esophageal lining to acidic gastric contents, which can lead to irritation and damage over time.

Several factors can contribute to or exacerbate reflux:
* Dietary choices: Spicy foods, acidic fruits, fried foods, alcohol, caffeine, and mint.
* Lifestyle habits: Smoking.
* Physiological states: Pregnancy.

The fundamental cause often involves the lower esophageal sphincter (LES), a muscular valve located at the bottom of the esophagus. Normally, the LES remains closed to prevent stomach acid from re-entering the esophagus. However, if this sphincter relaxes too frequently or inappropriately, stomach acid can escape into the esophagus, leading to reflux.

Common symptoms of reflux include:
* A bitter taste in the mouth (often after meals, at night, or when lying down).
* Bloating, indigestion, and belching.
* A burning sensation in the stomach or a painful burning in the chest (heartburn).
* Difficulty swallowing, nausea, bad breath, loss of appetite, and a chronic cough.