Fever, cough, and diarrhea are the three major symptoms of disease in pediatrics, accounting for more than 90% of the causes of outpatient emergency department visits. The fact that these manifestations are symptoms and not diseases suggests one thing: they can occur in many diseases. In other words, the three symptoms, fever, cough and diarrhea, can occur simultaneously in the same disease, or at different stages of the course of the disease, and can be the main manifestations of different diseases. Today, I will briefly talk about diarrheal diseases. I hope that through my explanation, parents will understand the causes, course, treatment and care priorities of diarrhea. Diarrhea, in simple terms, is a change in the number and nature of bowel movements. In other words, a normal person has one shaped bowel movement per day, and even if it becomes 2-3 bowel movements, it cannot be considered diarrhea as long as it is of normal nature. The causes of diarrhea are broadly the following three: 1, intrinsic factors 2, infectious factors 3, non-infectious factors. Intrinsic factors, mainly refers to the immaturity of the digestive system function during infancy, heavy load, prone to dysfunction and gastrointestinal tract infections, which is not difficult to understand and need not be repeated. Infectious factors refer to diarrhea caused by internal and external infections of the intestinal tract. Infections in the gastrointestinal tract are better understood, such as the common rotavirus enteritis, which is a watery diarrhea caused by rotavirus infection. Bacterial dysentery is diarrhea caused by Bacillus dysenteriae infection, and so on. Extra-intestinal infections can also cause diarrhea, such as upper respiratory tract infections, pneumonia, pyelonephritis, otitis media, skin infections and other acute infectious diseases in children. Non-infectious factors are mainly dietary, climatic and allergic factors. Improper feeding is one of the main causes of diarrhea. Excessive and premature feeding of large amounts of starchy and fatty foods, sudden changes in food varieties and weaning can all lead to diarrhea. The sudden change of climate, which increases intestinal peristalsis and decreases the secretion of digestive enzymes and gastric acid, can induce diarrhea. Some malabsorption syndromes such as lactose intolerance, glycogenic diarrhea, congenital chloride diarrhea, hereditary fructose intolerance, cystic fibrosis of the pancreas, and primary intestinal malabsorption can cause diarrhea. In people with milk protein allergy, watery diarrhea occurs 48h after eating cow’s milk. Diarrheal diseases are divided into three main categories according to the duration of the disease: 1, acute diarrheal disease (disease duration within 2 weeks) 2, migratory diarrheal disease (disease duration 2 weeks-2 months) 3, chronic diarrheal disease (disease duration more than 2 months), according to the severity of the disease can be divided into three types, namely, light: no dehydration, no toxic symptoms; medium: mild to moderate dehydration or toxic symptoms; heavy: severe dehydration or significant toxic symptoms (irritability, depression, drowsiness, pallor, high fever or temperature not rising, significantly higher white blood cell count, etc.). The clinical manifestations of diarrhea vary from cause to cause, and some diarrhea even has unique clinical manifestations. With the intricate causes and clinical manifestations of diarrhea, what are the main issues that parents should pay attention to? I think we should pay attention to the following points: (a) The presence of internal environmental disorders: In children with acute diarrheal disease, dehydration, electrolyte disorders and acid-base imbalance are easily caused by severe vomiting and diarrhea, refusal to eat and fever at the beginning of the disease, which must be corrected immediately. If parents see children with depression, poor facial color, dry mouth and urine, or even babbling and convulsions, they should immediately consult a doctor. (ii) Any nutritional development affected: For many children with prolonged and chronic diarrhea, the baby’s nutritional absorption and growth and development are more obviously affected. This is also a headache for many parents. On the one hand, they want to feed their babies better and supplement their nutrition, but on the other hand, they have diarrhea as soon as they eat certain things or eat more certain foods, and their weight gain is slow or even negative, and over time, malnutrition will occur. At this time, I hope that the family should not blindly supplement nutrition, but should take the child to the hospital and actively improve the examination to find the cause of diarrhea, such as the presence of milk protein allergy, lactose intolerance, primary intestinal malabsorption, etc. (iii) How to take oral rehydration: Acute diarrhea tends to cause disturbances in the internal environment of the affected child within a short period of time, so dehydration and electrolyte disturbances should be actively prevented and treated. Generally speaking, oral rehydration is the first recommended treatment for children with mild to moderate dehydration, as long as the vomiting is not severe. There are many methods, the simplest of which is oral ORS solution. Since oral rehydration salts (ORS) solution is slightly unpleasant to taste, many children have difficulty taking it orally, so it is recommended that the family be patient and let the child drink as much as possible. If there is frequent vomiting, you can temporarily fast from food and drink for 1-2h before feeding ORS solution. If there is no ORS at home, rice soup with salt solution (500ml of rice soup + 1.75g of fine salt or 25g of fried rice flour + 1.75g of fine salt + 500ml of water, cooked for 2-3min) can be given at a dosage of 20-40ml/kg for 4h, and then given orally at any time and as much as you can drink. (D) Is infusion faster recovery? Generally speaking, infusion does not stop diarrhea. Of course, intravenous infusion is the main means to rescue severe diarrhea, and its purpose is to correct the patient’s dehydration and electrolyte disorder and improve acidosis as soon as possible. For general mild diarrhea, intravenous fluids are not necessary. Most of the acute diarrhea in infants and children is related to intestinal infection and gastrointestinal dysfunction, and infusion cannot shorten the course of the disease. (E) Diet during diarrhea: Many families ask the question of whether to eat or not to eat during diarrhea, and what to eat. In general, it is recommended to continue the diet. The previous “starvation therapy” is actually not good for the child’s recovery. Therefore, during diarrhea, children are encouraged to continue eating, but they should avoid cold, greasy and stimulating foods, as well as foods with high sugar content and rich in crude fiber, and focus on light, easily digestible and less gas-producing foods. Supplementation with vitamin- and zinc-rich preparations is more conducive to recovery of intestinal function. (f) Do I need to use antibiotics for routine stool examination suggesting 3-5 WBC/hp and occult blood (±)? In many cases, the stool examination of children with diarrhea indicates 3-5 WBC/hp and occult blood (±), and other indicators are normal. Even when viral enteritis is severe, there can be a high WBC and positive occult blood, and the WBC will soon return to normal when the stool is rechecked. (G) How to take anti-diarrheal drugs? There are two types of antidiarrheal drugs commonly used, namely montelukast and intestinal probiotics, and there are also other drugs such as abscisicadotril and ellagitannin. Remember that montelukast should not be mixed with drugs, and should be taken on an empty stomach for good effect. Probiotics generally can not be heated at high temperature, and generally not taken at the same time with antibiotics. Demodex can reduce the secretion of intestinal glands and has good effect on watery stool, but it is prohibited in bacterial enteritis. I hope that my explanation will help families understand some knowledge about diarrhea and apply it in their future lives.