Light micrograph section through human stomach tissue showing coeliac disease. Coeliac disease is a condition where the body's immune system attacks its own tissues after consuming gluten. This damages the gut (small intestine) where it is unable to take in nutrients. This disease can cause a range of symptoms, including diarrhoea, abdominal pain and bloating. Coeliac disease is caused by an adverse reaction to gluten, which is a dietary protein found in cereals such as, wheat barley and rye.