Coeliac disease is caused by a reaction to gluten, a group of various proteins found in wheat and in other grains such as barley and rye. Moderate quantities of otes, free of contamination with other gluten-containing grains, are usually tolerated. The occurrence of problems may depend on the variety of oat. It occurs in people who are genetically-predisposed. Upon exposure to gluten, an abnormal immune response may lead to the production of several different autonomic that can affect a number of different organs. In the small bowel, this causes an inflammatory-reaction and may produce shortening of the villi lining the small intestine (vilious atrophy ).This affects the absorption of nutrients, frequently leading to anaemia.