Hypersensitivity reaction against patent blue during sentinel lymph node removal in three melanoma patients

Background In order to identify the sentinel lymph node (SLN) in melanoma patients intradermal injection of a radiocolloid tracer and a blue dye are commonly used. Life-threatening side effects such as allergic reactions to the injected dye have been described. We report 3 cases with systemic allergic reactions. Methods Three patients suffering from systemic reactions such as hypotension and rash during SLN biopsy were tested for sensitisation against patent blue and methylene blue with skin prick, scratch, and intradermal test. Results All 3 patients showed positive skin tests to patent blue confirming allergic reaction to the injected dye. In addition, all patients showed positive skin tests with methylene blue indicating immunologic cross-reactivity between patent blue and methylene blue. Conclusions Although allergic reactions to blue dye during SLN biopsy are rare, they may be life threatening. It is important that the attending anesthetist is aware of this.