linzess treats adults with ibs with constipation or chronic constipation. it can help relieve your belly in, and lets you he moreent frequand comps that are easier to pass. do not give linzess to children under six and it should not be given to children six to seventeen. it may harm them. don t 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 about managing your symptoms proactively with linzess.