Coeliac disease affects the small intestines. The lining of your small intestines is made up of tiny finger-shaped projections called villi. If you have coeliac disease and eat foods containing a protein called gluten, your villi become inflamed, fade off and flatten. The damage caused decreases the surface area of the villi and stops your small intestines from absorbing nutrients and minerals from your food properly. Coeliac disease is not an allergy or food intolerance; it's an autoimmune condition.
Attribution: BUPA