Background – Available epidemiology data on mustard allergy have not been updated in the last 20 years, while such food remains considered as an important source of severe reaction and is required to be notified on food labels in the European Union. The present study aimed to evaluate the real epidemiology of mustard allergy, proven by oral food challenge (OFC), and the severity of recorded reactions. Methods – We conducted a retrospective observational study at the Allergy Department of Montpellier University Hospital, including children and adults undergoing an OFC for suspected IgE-mediated mustard allergy between 2000 and 2024. The primary objective was to assess the prevalence of proven mustard allergy; secondary objectives included evaluating the diagnostic performance of clinical history and associations between specific IgE levels and clinical variables. Results – 86 patients (mean age 7.7 years, 77.9% males) were included in the present cohort. Twenty-five reported a prior mustard allergy clinical history, mostly mild grade 1 cutaneous reactions; 8 reported a history of non-severe anaphylaxis. The rest of them were sensitized to mustard but did not experience any previous reaction. In the whole cohort, only one patient (1.2%) reacted during OFC, with generalized urticaria. Conclusion – Mustard has long been considered a major food allergen, but our findings, as well as those available in the literature, suggest that proven IgE-mediated mustard allergy is rare and severe reactions are exceptional. These updated data encourage to perform a complete allergy work-up to avoid overdiagnosis and question the relevance of maintaining mustard as a mandatory allergen in food labeling.