New Challenges in Drug Allergy: the Resurgence of Excipients

PURPOSE OF REVIEW: Allergy to excipients is a cause of multidrug allergy and if it is not taken into account, it can lead to unexpected severe reactions. If an excipient allergy is suspected, an accurate examination followed by algorithms is very important for a correct diagnosis and to give patients detailed information in order to avoid future reactions. RECENT FINDINGS: In recent times, due to allergy COVID vaccine reactions, interest in excipients as polyethylene glycol derivatives (PEGs) has increased as a possible cause of drug and vaccine hypersensivity. In addition to PEGs many other excipients as gelatin, alpha-gal, protamine, benzalkonium chloride, and benzyl alcohol have been described as a cause of allergy to drugs and vaccines. For most excipients, the dilutions used for skin testing (ST) are not standardized and proper algorithms to reach a diagnosis are not available. SUMMARY: The purpose of this article is to review the excipients that may produce inmediate hypersensitivity drugs and vaccine reactions and update diagnostic procedures to reach an accurate diagnosis. We highlight the in vivo and in vitro diagnostic tests used in published reports and detail the dilution used for each excipient to perform ST in order to confirm this vital pathology and to prevent new reactions.