 The most common side effect is diarrhea, sometimes severe. If it's severe, stop taking Linzess and call your doctor right away. Other side effects include gas, stomach area pain, and swelling. Learn more at Linzess.com or call 1-800-LIN-Z-E-S-S. You can host the best backyard barbecue. When you find a professional on Angie to make your backyard the best around.