What are the symptoms of celiac disease?

Usually diarrhea. Celiac disease, among its many manifestations, may result in diarrhea. Simplistically, exposure of intestine to gluten causes inflammation of affected gut lining, with a decrease in absorptive surface of that gut, & resulting malabsorption of food. The best & most enduring fix is to avoid eating gluten. Serum tissue transglutaminase antibody can help determine how successfully gluten is avoided.