D1.42 - Unusual Delayed Hypersensitivity Reaction to Different Antibiotic Families

Introduction

Type IV delayed hypersensitivity reactions to antibiotics may present with discordance between

skin testing and clinical manifestations. In patients with suspected multiple drug sensitization,

controlled drug provocation testing can be decisive, provided it is performed under strict

allergology supervision.

Case Report

A 66‑year‑old woman with no previous allergy history underwent treatment with vancomycin and

piperacillin/tazobactam following surgery for an intraglottic abscess. Seven days after initiating

therapy, she developed a generalized maculopapular exanthem with mild pruritus and

subsequent desquamation. The eruption persisted for approximately three weeks.

Allergy Work‑up

Baseline tryptase was 6 ng/mL. Eosinophilia was documented during the episode (520–830/µL).

Liver enzymes and renal function remained within normal limits. Skin test results are summarized

in Table 1.

As part of the diagnostic evaluation, a controlled intravenous challenge with 1 g of vancomycin

was performed. No immediate reactions occurred; however, after 48 hours she developed a

generalized maculopapular rash, confirming a delayed hypersensitivity reaction, very likely due to

Type IV hypersensitivity to vancomycin

Diagnosis

Delayed maculopapular exanthem due to Type IV hypersensitivity to vancomycin, penicillin, and

piperacillin/tazobactam.

Conclusion

This case highlights the importance of integrating delayed‑reading skin tests with controlled

exposure testing when evaluating non‑immediate drug reactions, always weighing the

risk–benefit ratio. Reports of simultaneous hypersensitivity to vancomycin, penicillin, and

piperacillin/tazobactam remain scarce. Recognition of such patterns is essential for accurate

diagnosis and safe management of antibiotic therapy.