OBJECTIVES: Invasive fungal infections are increasing in frequency and are associated with high patient morbidity and mortality. The use of antifungal therapy is thus also increasing, and patients reporting hypersensitivity or allergic reactions to the limited antifungal agents currently available complicates management. There are no prior studies defining the incidence of antifungal allergies reported by patients. METHODS: A multicentre retrospective cohort review of all patient encounters at five large academic centres during 2023 was conducted. The primary outcome of this study was to find the prevalence of reported antifungal allergy across the University of California Health System, and secondarily determine the incidence of antifungal allergies among patients with documented administration of antifungal agent. RESULTS: A total of 1 704 176 patients were included and 2602 patients exhibited a documented antifungal allergy. Prevalences of antifungal allergies were: fluconazole 1591 (0.093%), general antifungal allergy 395 (0.023%), triazole 361 (0.021%), itraconazole 145 (0.008%), amphotericin 110 (0.006%) and flucytosine <
10 (0.001%). In the secondary outcome (incidence), 9829 patients received an antifungal agent and 298 reported an antifungal allergy (2.98%). CONCLUSIONS: Increasing age and use of antifungal therapy are associated with antifungal allergy prevalence. Antifungal allergy rates (prevalence and incidence) are also comparable to the rates reported for antibacterial agents and are highest with fluconazole.