Diarrhea in 18-month-old children may be caused by indigestion, which can be treated with dietary adjustments and oral rehydration salts; it may also be acute gastroenteritis, which requires electrolyte supplementation and antibiotic treatment. 1. Indigestion: you can actively adjust the diet to ensure that the child to eat some light and easy to digest food, but also pay attention to replenish fluids to avoid dehydration and shock. 2. Acute gastroenteritis: If the diarrhea is severe, it may lead to dehydration, and need to supplement fluids in time to avoid dehydration and shock. If it is a viral infection, it can be cured on its own without special medication; if it is combined with a bacterial infection, antibiotics such as amoxicillin are needed. All of the above medications should be used under the guidance of a doctor to avoid self-medication. 18-month-old children with diarrhea, there may be other reasons, it is recommended to go to the hospital in a timely manner, after clarifying the cause of the disease, under the guidance of the doctor to use drugs or other means of treatment.