Food intolerances are different than allergies and can cause malabsorption issues. My children have fructose intolerance. The first sign they ate something they shouldn't have is dark circles around their eyes. The gastroenterologist called then "allergy shiners". The second sign is irritability and frenzied running around. Then they have potty accidents. That night they have sleep issues. It all goes away after 3 days of avoiding their trigger foods.