Combined immunosuppression by immunomodulators and biological therapy has become standard in the medical management of moderate-tosevere inflammatory bowel disease (IBD) because of clearly demonstrated efficacy. Clinical studies, registries, and case reports warn of the increased risk of infections, particularly opportunistic infections; however, already in the steroid monotherapy era, patients are at risk because it is accepted that a patient should be considered immunosuppressed when receiving a daily dose of 20mg of prednisone for 2 weeks. Prescriptions increasingly involve azathioprine, methotrexate, and various biological agents. The TREAT registry evaluated safety in >6000 adult patients, half of them treated with infliximab (IFX) for about 1.9 years. IFX-treated patients had an increased risk of infections and this was associated with disease severity and concomitant prednisone use. The REACH study, evaluating the efficacy of IFX in children with moderate-to-severe Crohn disease, refractory to immunomodulatory treatment, reports serious infections as the major adverse events and their frequency is higher with shorter treatment intervals. The combination of immunosuppressive medications is a risk factor for opportunistic infections. Exhaustive guidelines on prophylaxis, diagnosis, and management of opportunistic infections in adult patients with IBD have been published by a European Crohn's and Colitis Organization working group, including clear evidence-based statements. We have reviewed the literature on infections in pediatric IBD as well as the European Crohn's and Colitis Organization guidelines to present a commentary on infection prophylaxis for the pediatric age group. Copyright © 2012 by European Society for Pediatric Gastroenterology.