Inflammatory bowel diseases, including Crohn disease and ulcerative colitis, are most often diagnosed during adolescence and young adulthood, with a rising incidence in pediatric populations. Infliximab is an effective treatment option for Crohn disease and ulcerative colitis. The most common adverse event with infliximab is an infusion reaction. Patients are often treated prophylactically with combinations of acetaminophen, intravenous steroid, and an antihistamine to prevent an infusion reaction. There is a high degree of practice variation regarding pretreatment for infliximab infusions, the efficacy of pretreatment with an antihistamine is unproven in preventing infusion-related reactions, and there is no national clinical standard. Unnecessary pretreatment in adolescence and young adulthood may be harmful, as this is a time to focus on developing self-care management skills. Antihistamine side effects including somnolence and dizziness may adversely affect adolescents and/or young adults' ability to complete schoolwork, drive, and transition toward autonomous management of their chronic illness. This report presents the findings of an evidence-based practice project reviewing the efficacy of pretreatment with an antihistamine in patients with Crohn disease and ulcerative colitis receiving infliximab. Practice implications are discussed.