Cross allergenicity between penicillins and cephalosporins

Twenty patients excluded from pre-marketing trials of cephalosporin antibiotics as chemoprophylaxis for open heart surgery were enrolled in an evaluation of skin-test reactivity. All gave a history of type I hypersensitivity to penicillins. None knew of adverse reactions to cephalosporins. Eighteen were negative to testing with saline, cefazolin, ceftriaxone, penicillin G and benzyl-penicilloyl. Two patients with positive skin tests safely received vancomycin chemoprophylaxis. We conclude that most patients who give a positive allergic history but have negative skin tests can safely receive cephalosporin chemoprophylaxis.