Which allergy should the nurse inquire about for a client allergic to penicillin?

When a client is allergic to penicillin, it is essential for the nurse to inquire about a potential allergy to cephalosporins. This is due to the structural similarities between penicillins and cephalosporins, which can lead to cross-reactivity. Both drug classes share a beta-lactam ring, and individuals allergic to penicillin may experience allergic reactions when treated with cephalosporins, even if the specific cephalosporin used has a different side chain structure.

This essential cross-reactivity stems from the immune system's ability to recognize small changes in the molecular structure of drugs, which can trigger the same allergic response. As a precaution, healthcare providers often assess the patient's history of penicillin allergy prior to prescribing cephalosporins to avoid any potential adverse reactions.