A 60-year-old client about to start IV cefazolin for surgical prophylaxis tells the nurse, "I had hives all over after amoxicillin 20 years ago." Which is the most appropriate nursing action?

Historical estimates of penicillin-cephalosporin cross-reactivity were as high as 10 percent, but this was confounded by early cephalosporin contamination with penicillin, by older first-generation drugs sharing more side chain similarity, and by including non-IgE rashes. Current data place overall cross-reactivity around 1 to 2 percent, and even lower for cephalosporins with side chains different from penicillin (cefazolin has a unique side chain and very low cross-reactivity). However, true penicillin anaphylaxis (urticaria, angioedema, wheezing, hypotension) deserves caution and is not the same as a remote rash. Standard nursing approach: (1) collect a detailed allergy history — what reaction, how long ago, what severity, what was done — and document accurately, (2) communicate with the prescriber and pharmacy to determine whether the original reaction was non-severe (delayed maculopapular rash, GI symptoms) versus severe (IgE-mediated anaphylaxis or SJS/TEN), (3) for non-severe history, cefazolin and most third- to fifth-generation cephalosporins are usually acceptable; for severe IgE history, options include allergy consultation, a test dose under monitoring, or an alternative agent (vancomycin, clindamycin, or other depending on indication), (4) avoid blanket avoidance of all beta-lactams which removes important treatment options. Refusing all beta-lactams, ignoring the history, and pretreating with diphenhydramine without reassessment are inappropriate.

Penicillin-cephalosporin cross-reactivity is overstated historically. Document and communicate; do not blanket-avoid or blanket-give without assessment.