Blood products are living tissue and are used in patient care. Blood components include whole blood itself, packed red blood cells, fresh frozen plasma, cryoprecipitate, platelets, granulocyte components, and Rhogam. Because whole blood and blood components come from human blood, there is a risk of infectious disease transmission despite meticulous screening. Blood components may contain small amounts of immunizing substances and other components. Because of risks, the need for transfusion should be specific.