 Do not give Linzess to children less than two. It may harm them. Do not take Linzess if you have a bowel blockage. Get immediate help if you develop unusual or severe stomach pain, especially with bloody or black stools. 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. Talk to your doctor and learn more at Linzess.com or call 1-800-LINZESS. Texting enrolls you in a recurring automated marketing text messages consent are required to purchase message and data rates may apply.