There are many benefits to using medications for Crohn’s disease or ulcerative colitis such as controlling symptoms, and in the case of anti-TNFs (i.e. Remicade, Humira, etc.), reducing the risk of surgery or hospitalization, and healing the intestines. It’s important, however, to know about the common side effects of these medications as well.
For less common but important risks you should know about, check out this article about rare side effects of medications for Crohn's and colitis.
There are also some less common but important risks you should know about. You can read about them here: Rare Side Effects of Medications for Crohn’s Disease and Ulcerative Colitis
Source: Siegel, C. A. Review article: explaining risk of inflammatory bowel disease therapy to patients. Aliment Pharmacol Ther 2011; 33: 23-32