Wheat allergy. Conceptual image of a woman holding a glass sphere containing ears of wheat (Triticum sp.). This could represent wheat allergy or coeliac disease. Wheat is one of the most common causes of food allergy. Sufferers are intolerant to gluten, a protein found in wheat. Ingestion of wheat or wheat products causes an immune response resulting in a rash, itching, swelling and, more severely, breathing difficulties or collapse. Delayed allergic reaction to wheat-containing foods can cause diarrhoea, bloating and anaemia, which result in malnutrition. Coeliac disease is a non-allergic reaction to gluten that causes malformation of the lining of the intestine.