The most common immediate adverse reactions to transfusion are fever, chills and urticaria. The most potentially significant reactions include acute and delayed haemolytic transfusion reactions and bacterial contamination of blood products.
Penicillin allergy is an overreaction by your immune system to penicillin and other antibiotics in the beta-lactam family and closely related antibiotics. Doxycycline belongs to a class of drugs called Tetracyclines. Tetracyclines are unrelated to penicillins and therefore safe to take in hypersensitive patients. Other unrelated antibiotics include quinolones (e.g. ciprofloxacin), macrolides (e.g. clarithromycin), aminoglycosides (e.g. gentamicin) and glycopeptides (e.g. vancomycin).
Doxycycline is part of a class of drugs called tetracyclines. It decreases bacteria's ability to make protein, which bacteria need to live. This activity does not directly kill the bacteria, but it does inhibit their growth and multiplication, which gives the immune system a chance to fight the infection.