The Patent Blue V Paradox: Hidden Offender, Serial Culprit

<u><b><i></i></b></u> <u><b><i>Background:</i></b></u> Patent Blue V (PBV) is extensively used in sentinel lymph node identification in cancer surgery, potentially leading to an increased incidence of hypersensitivity reactions. <u><b><i>Methods:</i></b></u> A retrospective analysis was conducted on patients with suspected PBV hypersensitivity, at our center from 2010 to 2023. Skin prick tests (SPT) were performed on all patients, followed by intradermal tests (IDT) if SPT was negative. <u><b><i>Results:</i></b></u> Of 160 patients with suspected perioperative hypersensitivity reactions (POH), 15 (9.4%) had received PBV. All patients were female, with a median age of 50 years. None had been previously exposed to PBV. In 2 cases, there was no registry of PBV use. In vivo tests were mostly performed 6-9 months after the index reaction (53%). PBV allergy was confirmed in 80% of cases via positive skin tests (SPT [<i>n</i> = 10] or IDT [<i>n</i> = 2]). In PBV allergic patients, anaphylaxis occurred in 7 patients (58%). A rising incidence of PBV allergy in the POH setting was observed from 2010 to 2023. <u><b><i>Conclusions:</i></b></u> PBV is a significant allergen in POH, with increasing incidence. SPT is effective and frequent enough for diagnosis, suggesting an IgE-mediated mechanism. Despite its allergenic potential, PBV's clinical utility supports its continued use with appropriate precautions.