Background: Isosulfan blue dye, or Lymphazurin, is commonly used for sentinel lymph node biopsy during operative procedures for patients with breast cancer. Allergic reactions to Lymphazurin have been reported, ranging from mild dermatologic reactions to severe anaphylaxis. Case Series: We report 2 patients who experienced allergic reaction to Lymphazurin while admitted to our service. We also conducted a literature search for similar cases using national databases. Included studies were limited to retrospective studies, case series, or case reports. Patient characteristics, reaction observed, and hospital course were extracted. Of the patients we report, both had grade 3 anaphylactic reactions requiring vasopressors to achieve hemodynamic stability. One patient required intensive care unit monitoring for 18 hours, and the other required overnight monitoring in the postanesthesia care unit. The literature revealed 29 studies reporting 108 patients with confirmed allergic reactions to Lymphazurin. Including the 2 patients in this series (total study n=110), most reactions were grade 3 (57/110, 51.8%), followed by grade 1 (40/110, 36.4%) and grade 2 (13/110, 11.8%). Among the patients who had individual hospital course reported (n=34), 23 patients required admission to the surgical intensive care unit. Of studies that reported cancellation or progression of surgery after the reaction, the surgical procedure was canceled for 12 of 26 patients (46.1%). Conclusion: Although severe anaphylactic reactions are more commonly reported, mild reactions occur more frequently but are likely underreported. Although no fatalities were reported in the cases included in this review, anaphylactic reactions to Lymphazurin pose significant risks. Operating room personnel should be familiar with potential reactions to recognize and treat them early.