ABSTRACT
Hypersensitivity to cholecalciferol (vitamin D3) or its active metabolite, calcitriol, is an exceedingly rare clinical phenomenon, with only 2 previously reported cases of suspected immediate hypersensitivity. Diagnosis of delayed drug hypersensitivity reactions is inherently difficult due to the lack of any robust in vitro diagnostic assay, particularly in those patients for whom provocation testing confers an unacceptable risk. In these situations, diagnosis relies on reproducible clinical manifestations following administration of the culprit agent, resolution upon its withdrawal and exclusion of other potential differential diagnoses. Based on these criteria, we propose the first reported case of delayed hypersensitivity to cholecalciferol successfully managed with a desensitisation protocol to pure cholecalciferol.