Which type of adverse reaction is characterized by a severe allergic response to blood products?

Anaphylaxis is a severe, life-threatening allergic reaction that can occur rapidly following exposure to allergens, including certain components in blood products. This reaction is characterized by a variety of symptoms such as difficulty breathing, swelling of the throat, hives, and a significant drop in blood pressure. In the context of blood transfusions, individuals who have a history of allergies may experience anaphylaxis due to proteins or antibodies present in the donor's blood.

In contrast, the other types of adverse reactions listed are distinct from anaphylaxis. Acute hemolysis refers to the rapid destruction of red blood cells following a transfusion, generally due to ABO incompatibility. Febrile non-hemolytic reactions involve fever and chills and are caused by the recipient's immune response to white blood cells or cytokines in the blood product rather than an allergic mechanism. Delayed hemolytic reactions occur days to weeks after transfusion, often due to the recipient's immune response to new red blood cell antigens, but are not classified as allergic reactions.

Thus, anaphylaxis stands out as the correct answer due to its classification as an acute and severe allergic response specifically linked to blood products.