An allergic transfusion reaction is when a blood transfusion results in allergic reaction. It is among the most common transfusion reactions to occur. Reported rates depend on the degree of active surveillance versus passing reporting to the blood bank.[1][2] Overall, they are estimated to complicate up to 3% of all transfusions.[3] The incidence of allergic transfusion reactions is associated with the amount of plasma in the product.[3] More than 90% of these reactions occur during transfusion.