Wonderbelly Antacid’s active ingredient is calcium carbonate. Calcium carbonate is an antacid that can relieve heartburn, acid indigestion, sour stomach, and upset stomach associated with these symptoms and is found in many of the leading brands on the market such as Tums, Rolaids, and Alka-Seltzer. If you are experiencing other symptoms or your symptoms persist for more than two weeks, you should consult with your doctor or pharmacist to determine the appropriate treatment option.