The blackening of blood vessels after chemotherapy is considered to be chemotherapy drug-associated phlebitis, which may change the puncture site or leave an intravenous catheter in place for a long period of time. Most chemotherapeutic drugs are fed into the patient’s body through intravenous infusion or intravenous injection to effectively inhibit the growth and proliferation of tumor cells. If the same blood vessel is punctured for a long time and repeatedly, the chemotherapy drugs will cause stimulation to the endothelium of the blood vessel, leading to the emergence of aseptic inflammation, thus triggering chemotherapy drug-associated phlebitis, which is manifested by the deepening of the color of the blood vessel, and it is recommended to change the puncture site of the chemotherapy or leave the intravenous catheter in place for a long time. It is recommended to change the chemotherapy puncture site or leave an intravenous catheter in place for a long period of time. It is recommended to give feedback to the supervising doctors and nurses as soon as possible to change the chemotherapy puncture site in order to avoid further aggravation of the local irritation.