A mild allergic reaction (urticarial) is one of the most common transfusion reactions
occurring in approximately 1% to 5% of all transfusion recipients. The symptoms are mild
and generally easy to treat.
Allergic symptoms during a transfusion are caused by recipient reactions to plasma
proteins in the blood or component unit.
Signs and Symptoms
A mild allergic reaction can occur anytime during the transfusion to 1 hour post transfusion. Signs and symptoms of a mild allergic transfusion reaction are limited to:
A mild allergic reaction is easily identified by the classic signs and symptoms listed
above. More severe signs or symptoms of any other nature should be carefully assessed to
determine the cause and subsequent treatment.
Symptoms associated with mild allergic reactions may be decreased by slowing the rate of transfusion. (The rate of the transfusion may be increased later if symptoms subside.) An antihistamine may be ordered to relieve the patients symptoms. Antihistamines may be ordered prophylactically if the patient experiences recurrent urticarial reactions. If symptoms worsen or recur later in the transfusion, the transfusion may need to be to discontinued if antihistamines do not alleviate the patients symptoms. Epinephrine may be indicated for severe persistent urticaria associated with bronchospasm. (See Anaphylactic Reactions). When allergic reactions occur despite pre-transfusion antihistamine, washed cells may be indicated. If allergic reactions are severe or persist despite premedication, consult with Puget Sound Blood Center Physician on Call at 206-292-6525.