Celiac Disease is an autoimmune disorder that affects the small intestine. It occurs when the body reacts negatively to gluten, a protein found in wheat, barley, and rye. This reaction damages the lining of the intestine, leading to malabsorption of nutrients and various gastrointestinal symptoms, such as diarrhea, bloating, and abdominal pain. Diagnosis typically involves blood tests and a biopsy of the small intestine. The only effective treatment is a strict, lifelong gluten-free diet, which helps heal the intestine and prevents further complications. Individuals with Celiac Disease must avoid foods containing gluten to maintain their health.