# Immediate Hypersensitivity Reaction to Pheniramine in a Case of Multiple Drug Hypersensitivity Syndrome

## TL;DR

This paper presents a rare case of a patient with multiple drug allergies, including an unusual hypersensitivity to the antihistamine pheniramine.

## Contribution

The novelty lies in identifying pheniramine as a rare cause of hypersensitivity in a patient with multiple drug allergies.

## Key findings

- The patient exhibited hypersensitivity to multiple chemically unrelated drugs, including pheniramine.
- Skin and provocation tests confirmed the diagnosis of multiple drug hypersensitivity syndrome and pheniramine allergy.
- The case highlights the importance of considering antihistamines in MDHS evaluations when history suggests it.

## Abstract

Multiple drug hypersensitivity syndrome (MDHS) is a rare condition characterized by hypersensitivity reactions to at least two chemically unrelated drugs. While non-steroidal anti-inflammatory drugs and antibiotics are the most commonly implicated agents, hypersensitivity to antihistamines is extremely rare. A comprehensive approach, including detailed patient history, skin testing, and drug provocation tests, is essential for the accurate diagnosis and management of MDHS, particularly in patients with multiple drug reactions. When evaluating MDHS, antihistamines should also be considered as potential culprits if suggested by the patient’s history. Here, we aimed to present a case of a patient who reported allergic reactions following the administration of diclofenac sodium, paracetamol, COVID-19 mRNA vaccine, clarithromycin, and pheniramine hydrogen maleate. Based on the skin and provocation tests we performed, the patient was diagnosed with multiple drug hypersensitivity along with pheniramine allergy.