Chemotherapy is the short name of chemical drug treatment, which kills cancer cells through the use of chemotherapeutic drugs to achieve the therapeutic purpose. Chemotherapy is one of the most effective means of cancer treatment at present, and is one of the three major means of cancer treatment together with surgery and radiotherapy. Surgery and radiotherapy are local treatments, which are only effective for tumors at the treatment site, but it is difficult to effectively treat potential metastatic foci (cancer cells that have actually metastasized but cannot be detected clinically due to the limitations of current technology) and cancers that have already undergone clinical metastasis. Chemotherapy is a means of systemic treatment, and no matter what route of administration is used (oral, intravenous and body cavity administration, etc.), chemotherapeutic drugs will spread to most of the organs and tissues of the whole body along with blood circulation. Therefore, chemotherapy is the main treatment for some tumors with systemic dissemination tendency and middle and late stage tumors that have already metastasized. Chemotherapeutic drugs do not have specific targeting, it is only aimed at the fast-growing cells to inhibit the effect. Tumor cells grow particularly fast, they are cells with particularly vigorous growth capacity, and chemotherapeutic drugs will kill them when they enter the human body. There are also some normal cells in the human body that grow very fast, and chemotherapeutic drugs will also work on them: 1. Hair: Hair grows every day. So after chemotherapy drugs enter the body, all the fast-growing cells are inhibited, including both abnormal tumor cells and some normal growth cells, which will cause hair loss. 2, intestinal mucosa: intestinal mucosa is renewed every day, but also relatively fast-growing cells, so chemotherapy drugs into the body will also damage these cells, causing nausea and vomiting. Overall, what parts of the body grow faster, chemotherapy drugs will have an impact on this part.