Fluorouracil is an anti-metabolic chemotherapeutic drug, which is mainly used clinically for colorectal cancer, gastric cancer and other tumors of the digestive system, breast cancer, gynecological tumors, head and neck squamous cancer, etc. For cancerous thoracic ascites, the drug can be administered locally. The common side effects after applying fluorouracil are as follows: 1) Gastrointestinal reactions, patients show nausea, vomiting, loss of appetite, oral mucositis, abdominal pain, diarrhea, etc. 2) Bone marrow suppression, mainly manifested as a decrease in white blood cells and platelets, which can be recovered 2 weeks after stopping the drug. 3) Hepatotoxicity, because the drug is metabolized in the liver, which can cause reversible liver damage. 4) Local The effect of injected drug can appear phlebitis, many patients appear skin pigmentation, skin pigmentation is mostly seen in the face, nails, etc. 5, alopecia dermatitis performance. 6, cardiotoxicity, especially for patients with previous coronary heart disease and other underlying diseases is particularly obvious.