Decoding Beta‐Lactam Cross‐Reactivity – Longitudinal Patch Testing From 2000 to 2022

PT is useful to confirm a probable culprit in ni-CADR to βL. Co-reactivity, interpreted mostly as cross-reactivity, occurred within cephalosporin and, particularly, with penicillin subclasses, including between piperacillin-tazobactam and remaining penicillins, which has seldom been described. There was no association between penicillins and cephalosporins as a whole, except between aminopenicillins and aminocephalosporins, attributable to a similar lateral chain amino group. We found an unexpected association between meropenem and ceftriaxone, probably a concomitant sensitization.