Four-year-old children who have diarrhea can take probiotics orally to regulate the intestinal flora. If the stool is relatively thin, you can take oral montmorillonite, which, when taken orally, can form a protective film on the surface of the gastrointestinal tract, thus drying up the stool. In addition, you can take oral rehydration salt, which contains electrolytes, and after drinking it with water according to the instructions, it can prevent mild to moderate dehydration. If the stool contains mucus or even pus and blood, the stool that looks bad should be taken to the hospital for laboratory tests. If the stool routine suggests the presence of bacterial infection, oral antibiotics should be taken under the guidance of a doctor, or if it is serious and causes bacteremia and high inflammation in the blood, intravenous antibiotic treatment may be required. The above questions are for reference only, please refer to the doctor’s face-to-face guidance for specific medication and treatment.