not-yet-known not-yet-known not-yet-known unknown In this study we examined the frequency of allergic transfusion reactions in children and young adults over a seven-year period at Children’s Hospital of Michigan. There was a total of 62,982 transfusions during the study period and the transfused blood components included packed red blood cells (61.5%), platelet units (24.3%), fresh frozen plasma (10.1%) and cryoprecipitate units (4.1%). There were 120 allergic reactions (1 in 525 overall transfusions, 0.191%) in 90 recipients during the study period, with the highest rate noted for platelet units (1 in 356 platelet transfusions, 0.281%). Demographic records were available for 87 of the recipients and 95.4% had underlying hematologic or oncologic conditions. About half (50.8%) of the reactions were mild, causing only skin hives. Severe reactions tended to be more common with platelet units (60.5%). Epinephrine was used in the treatment of six of the reactions, rendering them anaphylactic reactions. The rate of allergic transfusion reactions reported in our study (0.191%) is much lower than the rates reported in the literature, suggesting under-reporting of allergic reactions.