Every summer and autumn is the peak season of diarrhea incidence in China, especially in recent years by the attack of tropical storms, rainfall increased significantly, the weather is hot and humid, conducive to the breeding of various bacteria, diarrhea patients is a sharp increase. Normal people defecate once every 1 day-3 days, and a few people are used to defecate 2~3 times a day, which is normal. If the number of stools increases, and the stool is thin or accompanied by an increase in the number of stools, it is called diarrhea. Diarrhea can be divided into acute diarrhea and chronic diarrhea. Acute diarrhea is mostly seasonal, and most acute diarrhea is due to infection, which occurs in the summer and autumn. Chronic diarrhea is defined as diarrhea that is recurrent or lasts for more than 2 months. The causes of chronic diarrhea are relatively more complex, and diagnosis and treatment are sometimes difficult. Many people think that diarrhea is just diarrhea, so it is not necessary to make a fuss about it because it is good for a few days. In fact, because chronic diarrhea is associated with a variety of diseases, if paralysis and carelessness are not taken seriously, it is easy to miss the hidden condition behind the diarrhea, delaying treatment and bringing serious consequences. Diarrheal diseases are a group of multi-pathogenic, multi-factor diseases, which are somewhat contagious and one of the three types of infectious diseases with the most incidence in China, and have long endangered human health. According to the World Health Organization (excluding China), there are about 1 billion people suffering from diarrhea worldwide every year. According to the etiology diarrhea is generally divided into two main categories, infectious diarrhea and non-infectious diarrhea. For infectious diarrhea, it is collectively called infectious diarrheal disease (or enteritis) until the etiology is clear, and after the etiology is clear, the diagnosis should be made according to etiology, such as bacterial dysentery, amoebic dysentery, cholera, Salmonella typhimurium enteritis, rotavirus enteritis, etc. For non-infectious diarrhea, the diagnosis can be made according to history, symptoms and examination analysis as food diarrhea, symptomatic diarrhea, allergic diarrhea, non-specific ulcerative colitis, glycogenic diarrheal disease, etc. Diarrhea attacks are often accompanied by abdominal pain, vomiting and other symptoms, which can cause malnutrition, vitamin deficiency, anemia and decreased body resistance for a long time. The most likely diagnosis for outpatients can be estimated based on the duration of diarrhea, stool characteristics, visual and microscopic examination of stool, season of onset, age of onset and prevalence. For example, there is a change in stool characteristics, with dilute, watery, mucus or pus-blood stools, and an increase in the number of stools than usual. Rotavirus enteritis is most likely in the fall and toxin-producing E. coli enteritis is most likely in the summer. In terms of disease duration, acute diarrhea generally lasts less than two weeks, delayed diarrhea lasts between two weeks and two months, and chronic diarrhea lasts more than two months. From the point of view of the disease, if there is no dehydration and no symptoms of poisoning, it is a mild diarrhea, and if there is severe dehydration or significant moderate symptoms, it is a severe diarrhea. In terms of age, diarrhea in children is more likely to be infections, disaccharidase deficiency, congenital chlorosis, and pancreatic fibrocystic degeneration; diarrhea in young adults is more likely to be functional diarrhea and ulcerative diarrhea; diarrhea in middle age or old age is often colon cancer. Many people think that diarrhea is a common disease and can be cured by taking some safranin or other antibiotics by themselves. In fact, a lot of diarrhea, especially chronic diarrhea, is not necessarily caused by intestinal diseases, but may be a manifestation of many other diseases, and should not be taken lightly in clinical practice. Other diseases that often cause diarrhea include: diabetes, hyperthyroidism, pancreatitis, pancreatic cancer, cholelithiasis, and post-cholecystectomy. Diabetes mellitus causes diarrhea associated with its resulting gastrointestinal vegetative neuropathy. Diarrhea is persistent and intermittent, with episodes lasting from a few days to a few weeks; intervals can last from weeks to months, and diarrhea can occur both day and night, and about 5% of patients with diarrhea also have steatorrhea. Patients with hyperthyroidism have frequent stools or even diarrhea due to rapid intestinal motility and poor digestion and absorption, and the stools are usually mushy and contain more undigested food. It is not uncommon to see diarrhea as the first symptom of hepatocellular carcinoma. The liver detoxification function of liver cancer patients decreases, and the intestinal mucosa produces intestinal toxins under the stimulation of harmful chemical substances, prompting mast cells to proliferate and release histamine, causing the intestinal mucosa to become degenerative and edematous, increasing permeability and reducing water reabsorption, resulting in a large amount of water discharged into the intestinal cavity and causing diarrhea. Most colorectal cancers occur after middle age, and those located in the left side of the colon often grow in a circular pattern, accompanied by changes in defecation habits. When the tumor has erosion, ulceration or necrosis, it can be manifested as diarrhea, bloody stool and shortness of breath. It starts slowly with abdominal pain and diarrhea, and gradually worsens, with loose or watery stools, often without pus and blood. Inflammation, increased peristalsis and secondary intestinal malabsorption of the diseased intestinal segment are the main causes of diarrhea. Most episodes are intermittent, with persistence later in the course of the disease. The diarrhea is caused by increased intestinal peristalsis and impaired absorption of water and sodium in the intestinal lumen under the stimulation of inflammation. In mild cases, the bowel movements are 3~4 times a day, or the diarrhea alternates with constipation; in severe cases, the bowel movements are frequent and the stools are mostly paste-like, mixed with mucus and pus and blood. Therefore, the appearance of chronic diarrhea should not be taken lightly, but should be carefully examined, and only when the cause of the disease is identified can the correct treatment be obtained. On the contrary, if only symptomatic treatment is given for chronic diarrhea, the effect is often poor, and even delays the condition and loses the best time for treatment. As the season of autumn diarrhea is high, many people think of bacterial infection as soon as they have diarrhea and immediately start taking various antibiotics as a smart move. In fact, fall diarrhea is mostly caused by rotavirus, so antibiotics are not only wrong, but also harmful. Diarrhea is not a minor problem, and patients should be careful with their medication. After diarrhea, the main thing is to adjust the diet and consciously replenish water and electrolytes. It is best to go to the hospital for oral electrolytes if possible; all serious patients should go to the hospital to confirm the diagnosis for symptomatic treatment.