We report a case of immediate allergic hypersensitivity following intra-articular injection of ioxaglate and cortivazol. Allergic hypersensitivity to ioxaglate was confirmed through skin test positivity. No cross-reactivity with the other skin-tested iodinated contrast agents was observed. Allergic hypersensitivity to cortivazol was ruled out. Flow cytometry-based basophil activation test corroborated with skin tests results. The detection of sensitized basophils by flow cytometry associated with the clinical history and skin tests can be useful to confirm the diagnosis of immediate allergic hypersensitivity and provide advice for further procedures. Finally, this case confirms the need for systematic allergological investigation in cases of immediate hypersensitivity, whatever the mode of drug administration, in order to avoid the culprit allergen in the future.