If someone has an allergy to gluten/grains, what occurs when they eat wheat anyway?

Gluten exposure. With celiac diease, consuming food/drink with gluten (wheat, barley, rye) cause inflammation in small bowel lining with resulting diarrhea, anemia, risk of small bowel lymphoma. Instead, enjoy products from rice, soy, oats. Liberalize fresh fruits & vegetables, as well as lean meats. Consider blood testing for tissue transglutaminase antibody to assess whether your diet is truly free of gluten.