Desensitization of patients with allergic reactions to immunosuppressives in the treatment of inflammatory bowel disease.

Crohn's disease and ulcerative colitis are chronic, immune-mediated inflammatory bowel diseases (IBDs) of unknown etiology with high morbidity in patients who are not receiving adequate medical treatment. A variety of medical therapies are currently available, and much progress has been made to alleviate symptoms and restore quality of life. The mainstay of treatment in those with moderate to severe disease consists of medications that alter or suppress the body's immunologic attack on its own gastrointestinal tract. The medications currently in use are highly effective when given in the appropriate clinical context, but side effects are not uncommon and must be treated expeditiously when they occur. One class of immunosuppressive medication, 6-mercaptopurine and its prodrug azathioprine, is effective at inducing remission and improving the lives of patients with IBD. The most common side effects of these drugs are allergic reactions and rarely can they be severe and life threatening. These reactions can sometimes be overcome by desensitizing the immune system to the drug. This review emphasizes allergy to 6-mercaptopurine and azathioprine and the process of desensitization when these allergic reactions occur in order to continue use of this important class of medication in the total treatment of IBD.