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

beta-Lactams which include penicillins, cephalosporins, carbapenems, and monobactams 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 beta-lactams in penicillin- or cephalosporin-allergic subjects by carrying out diagnostic tests with alternative beta-lactams and, if appropriate, graded challenges. Several studies demonstrated that cross-reactivity connected with the beta-lactam ring, causing positive responses to allergy tests with all beta-lactams, is infrequent in subjects with an IgE-mediated allergy and anecdotal in those with a T-cell-mediated allergy. Identities or similarities of beta-lactam side-chain structures are mainly responsible for cross-reactivity among these antibiotics. For example, in aminopenicillin-allergic subjects, cross-reactivity with aminocephalosporins 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 beta-lactams seem to indicate that prior exposures may be responsible for coexisting sensitivities. Therefore, pre-treatment skin tests with the related beta-lactams are suggested before administering them via graded challenges to beta-lactam-allergic patients who need alternative beta-lactams.

Automated summary

Beta-lactams are the most common antibiotics causing allergic reactions, with cross-reactivity usually due to similarities in side-chain structures. While positive responses to all beta-lactams are infrequent in patients with IgE-mediated allergies, they are anecdotal in those with T-cell-mediated allergies.