Question: What type of reactions are possible from the blue dye used in sentinel lymph node biopsy?
Answer: The most common reaction to the blue dye used during sentinel node mapping is to have some staining of the skin of the breast because it is a blue dye. That usually takes several weeks to go away. The patient may also note that their urine turns blue for about 24 hours because the blue dye is metabolized by the kidney.
Only about one percent of patients have a severe allergic reaction to the blue dye, and what we see in that circumstance is the development of blue hives -- they're like welts on the skin similar to mosquito bites -- or their blood pressure may drop, which usually responds to medication.