Coeliac disease is an autoimmune condition triggered by gluten, a protein found in wheat, barley, and rye. In affected individuals, gluten ingestion causes the immune system to attack the small intestine, damaging the villi responsible for nutrient absorption. This leads to symptoms such as diarrhoea, bloating, weight loss, anaemia, fatigue, and, in children, poor growth. Left untreated, it can increase the risk of osteoporosis, infertility, neurological problems, and certain cancers. The only effective treatment is a strict lifelong gluten-free diet, which allows intestinal healing, symptom resolution, and prevention of long-term complications.