What is the first sign of a transfusion reaction?

Fever or chills is the first sign of a transfusion reaction because these symptoms typically arise due to the immune system's response to foreign antigens present in the transfused blood components. During a transfusion, if the recipient's body recognizes the transfused blood as a foreign substance, it may trigger an inflammatory response, leading to an increase in temperature or chills. This immune response is often one of the initial indicators of a potential reaction, and early recognition is essential for ensuring patient safety.

Other options, such as nausea, vomiting, headache, dizziness, or skin rash, may occur later in the course of a transfusion reaction or in response to different triggers but are not typically the first signs to manifest. Identifying fever or chills promptly allows healthcare providers to intervene quickly and manage the reaction effectively.