The European Medicines Agency (EMA) defines excipients as the constituents of a pharmaceutical form apart from the active substance. Delayed hypersensitivity reactions (DHRs) caused by excipients contained in the formulation of medications have been described. However, there are no data on the prevalence of DHRs due to drug excipients. Clinical manifestations of allergy to excipients can range from skin disorders to life-threatening systemic reactions.
The aim of this study was to perform a literature review on allergy to pharmaceutical excipients and to record the DHRs described with various types of medications, specifically due to the excipients contained in their formulations. The cases reported were sorted alphabetically by type of medication and excipient, in order to obtain a list of the excipients most frequently involved for each type of medication.

Key words: Allergy, Delayed hypersensitivity reaction, Drug hypersensitivity reaction, Excipient, Pharmaceutical excipients