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.