β-Lactam Allergy and Cross-Reactivity: A Clinician’s Guide to Selecting an Alternative Antibiotic

Abstract

β-Lactams which include penicillins, cephalosporins, carbapenems, and mono-bactams are the most common antibiotic classes reported to cause allergic reactions to drugs. This review is mainly about published studies assessing the cross-reactivity among β-lactams in penicillin-or cephalosporin-allergic subjects by carrying out diagnostic tests with alternative β-lactams and, if appropriate, graded challenges. Several studies demon-strated that cross-reactivity connected with the β-lactam ring, causing positive responses to allergy tests with all β-lactams, is infrequent in subjects with an IgE-mediated allergy and anecdotal in those with a T-cell-mediated allergy. Identities or similarities of β-lactam side-chain structures are mainly responsible for cross-reactivity among these antibiotics. For example, in aminopenicillin-allergic subjects, cross-reactivity with ami-nocephalosporins could possibly be over 30%. On the other hand, in a few prospective studies of penicillin-allergic individuals, less than 1% of cases show a cross-reactivity between penicillins and both aztreonam and carbapenems. Particular patterns of allergy-test positivity observed in some studies that assessed cross-reactivity among β-lactams seem to indicate that prior exposures may be responsible for coexisting sensitivities. Therefore, pre-treatment skin tests with the related β-lactams are suggested before administering them via graded challenges to β-lactam-allergic patients who need alternative β-lactams.