Every afternoon nausea diarrhea is considered to be acute gastroenteritis, gastrointestinal dysfunction, colorectal cancer and other diseases caused by the need for targeted treatment under the guidance of a doctor to drug therapy, such as ciprofloxacin, montelukast and so on. 1. Acute gastroenteritis: If you eat unclean food at lunch, it can cause nausea and diarrhea every afternoon, with bacterial infection can be treated with ciprofloxacin, severe diarrhea can be treated with loperamide to stop diarrhea, and with symptoms of dehydration can be treated with rehydration. 2. Gastrointestinal dysfunction: abdominal pain, diarrhea, nausea and other symptoms can occur, severe diarrhea can be treated with montelukast to stop diarrhea, with neurological vomiting can be treated with vitamin B6, and severe vomiting can be treated with ipratropium and other drugs. 3. Colorectal cancer: symptoms such as change of bowel movement, abdominal discomfort, etc. need to consider surgical resection of tumor, and target drugs such as cetuximab, bevacizumab, etc. or radiotherapy can also be used. It is recommended to go to the hospital to consult the doctor for judgment and give treatment plan.