If a two-year-old baby has diarrhea, the first thing you can do is to take oral probiotics to regulate the intestinal flora. In addition, if the stool is relatively thin, you can take oral montelukast. Montelukast is a kind of intestinal mucosa protector, which can form a protective film on the intestinal mucosa when taken orally on an empty stomach, thus reducing the water from the cells to enter the intestine. In addition, if your baby needs to drink water, it is best to take oral rehydration salts. Oral rehydration salts are given to your child after mixing with water according to the instructions, which can help prevent the occurrence of dehydration and replenish some electrolytes lost from the stool. If the stool contains mucus or even pus and blood, or if the diarrhea is prolonged, the stool should be taken to the hospital for laboratory tests to see if there is a bacterial infection. If it is bacterial enteritis, you need to apply antibiotics under the guidance of your doctor.