Dias, LilianaNeves, Claudia2023-02-022023-02-022022-03Nascer e Crescer - Birth and Growth Medical Journal 2022;31(1):31-37. doi:10.25753/BirthGrowthMJ.v31.i1.20898http://hdl.handle.net/10400.16/2761Allergic reactions to beta-lactam antibiotics are the most common cause of allergic drug reactions. The incorrect diagnosis prevents patients from receiving a highly effective therapy. The potential cross-reactivity between penicillin and cephalosporin has very significant therapeutic implications. Penicillins and cephalosporins share a common beta-lactam ring and side chains. A number of studies indicate that the R1 side chain, rather than the ring itself, is the determining factor for cross-reactivity. Herein is presented a review of the immunologic mechanisms implicated in penicillin and cephalosporin cross-reactivity and a practical approach to the use of cephalosporins in patients allergic to penicillin.engcephalosporincross-reactivitypenicillinside chainjournal articlehttps://doi.org/10.25753/BirthGrowthMJ.v31.i1.216072183-9417