The gastrointestinal tract is susceptible to various disorders. If the lower esophageal sphincter is damaged, stomach acid can flow back into the esophagus, causing irritation and inflammation of the lining. This condition is called gastroesophageal reflux disease (known as heartburn) and may cause chest pain and difficulty swallowing. In the stomach, prolonged use of nonsteroidal anti-inflammatory drugs like aspirin, chronic alcohol consumption, bacterial infections such as Helicobacter pylori, or immunological reactions can harm the gastric mucosa. These changes can lead to inflammation of the stomach lining, resulting in gastritis, or they may erode the lining of the stomach or proximal duodenum, leading to the formation of peptic ulcers.

The immune disorder Celiac disease is triggered by consuming gluten found in wheat, barley, and rye. It damages the small intestine, resulting in symptoms such as diarrhea, weight loss, and fatigue.

Finally, irritable bowel syndrome is a complex gastrointestinal disorder caused by unexplained changes in gastrointestinal motility and stress. Bloating, nausea, and irregular bowel habits are additional symptoms of irritable bowel syndrome.