The reasons why breast cancer patients sweat a lot after chemotherapy and targeted drugs include the side effects of chemotherapy and targeted drugs, the decrease of estrogen level in the body, and the patients’ own poor physical condition. 1. The use of chemotherapy and targeted drugs will cause damage to the body of breast cancer patients, resulting in the decline of white blood cells, hemoglobin and other indicators, causing infections or anemia, which will lead to excessive sweating of breast cancer patients. 2. After chemotherapy and targeted drugs are administered to breast cancer patients, the estrogen level in the patient’s body will also decrease, leading to menopausal syndrome, which may also be manifested as sweating. 3. There are also patients with weak physical condition, surgery, chemotherapy and targeted drugs continue to damage the immunity of breast cancer patients, making their physical condition even weaker, which may also be manifested as sweating. It is suggested that patients should consult the doctor in time if they have any discomfort and take active treatment to avoid delaying their condition.