What are the common side effects of a blood transfusion?

Several possibly: Reactions to blood transfusions are very rare now with the techniques that we have to "crossmatch" blood. The most common reaction is have a rise in temperature. Next would be an allergic reaction. Most of these are not severe. The worst reaction is called a hemolytic reaction. These occur when there are important incompatibilities between your blood type and the type you have been given.

Rigors, fever: Rigors, occasionally fevers. Uncommon might be severe reaction. Anaphylaxis. Hperkalemia.

Immunologic or not: Causes for transfusion reactions may be immune related or not, also they can be acute (less than 24 hours) or delayed. These are some: hemolytic; febrile, non-hemolytic; bacterial contamination (septic shock); anaphylaxis; transfusion-related acute lung injury (trali); transfusion-associated circulatory overload (taco); graft vs. Host disease (ta-gvhd); iron overload; infections.

Common are trivial: We pathologists run the blood bank and are always enouraging prudent and sparing use of our product. There's a few percent chance you'll get the sneezies and/or the itchies, a bit less that you'll get a mild fever. The very serious side effects are much less common. The one that's most worrisome is lung damage from donor antibodies -- less now that we use donors less likely to have them.