If a one-and-a-half-year-old baby has diarrhea, the mothers need to promptly replenish the baby’s water and regulate the body by changing the baby’s complementary food. If the situation is serious, the baby needs to be sent to the hospital for examination, and the treatment is as follows: 1. promptly replenish the baby’s water, the balance of body fluids in the one-and-a-half-year-old baby’s body is relatively fragile, and once the diarrhea occurs, it is easy to cause dehydration in itself. 2. regulate the body through complementary food The baby’s diarrhea may be due to enteritis or viral infection, so it is important to do routine blood and stool tests at the hospital to clarify the cause and give the baby medication as prescribed by the doctor.