A nurse is monitoring a client who is receiving a blood transfusion. Which of the following findings indicates the client is experiencing an allergic reaction?

A. Client report of headache: Headache is a nonspecific symptom and may occur with fluid shifts or mild febrile reactions, but it is not a primary sign of an allergic transfusion reaction. It does not reliably indicate hypersensitivity to the transfused blood. B. Distended neck veins: Distended neck veins suggest fluid overload or heart failure rather than an allergic reaction. This finding is associated with increased central venous pressure and is unrelated to hypersensitivity responses. C. Marked hypertension: Elevated blood pressure can result from anxiety, pain, or fluid overload, but it is not characteristic of an acute allergic reaction to a blood transfusion. Allergic reactions typically do not cause significant hypertension. D. Onset of urticaria: The appearance of hives (urticaria) is a classic sign of an allergic reaction to a blood transfusion. It reflects a hypersensitivity response mediated by histamine release, often accompanied by itching and sometimes mild flushing, indicating that the immune system is reacting to proteins in the donor blood.