Methylene blue is a dark green to dark brown solid powder, with its aqueous solution appearing sky blue. Its core characteristic is redox chromogenic duality—it remains stable blue in oxidizing environments and turns colorless under reducing conditions. In the medical field, it is primarily used for intraoperative specific labeling of nerve and lymphatic tissues to enhance procedural precision. It assists in identifying ureteral fistulas or bladder integrity through the blue staining phenomenon of body fluids, providing visual support for medical assessment. Additionally, it can modulate the ion channel function of peripheral nerves to alleviate sensory abnormalities and exert regulatory effects on microbial environments.