What is a common sign of an allergic reaction during a blood transfusion?

An allergic reaction during a blood transfusion is typically characterized by symptoms related to the immune response towards certain proteins in the transfused blood. Itching or rash is a common sign of this kind of reaction. This occurs because the body’s immune system identifies these proteins as foreign, triggering histamine release, which can result in symptoms like hives, itching, or rashes on the skin. These symptoms often emerge shortly after the transfusion begins and are indicative of a mild allergic response.

While fever, nausea, and chills can occur during a blood transfusion, they are not specific to allergic reactions. Fever can indicate a febrile non-hemolytic reaction, often associated with the recipient's response to white blood cells in the transfusion. Nausea can occur due to various reasons, not limited to blood transfusions, and chills may accompany infections or other types of transfusion reactions. In contrast, itching or rash distinctly aligns with an allergic response, making it the hallmark sign in this context.