Infant fontanel collapse may be vomiting diarrhea, improper feeding, lack of water in the body and other reasons related to the specific analysis is as follows: 1. Vomiting and diarrhea: Vomiting and diarrhea will cause a large loss of body fluids, leading to a decrease in cerebrospinal fluid and a decrease in intracranial pressure, which will lead to the symptom of collapsed fontanel. 2. Improper feeding: Improper feeding leads to severe malnutrition in infants and extreme wasting of the body, which can lead to the symptoms of fontanel collapse. 3. Lack of water: If the baby has not been hydrated for a long time, resulting in lack of water in the body, the symptoms of fontanel collapse will appear, after timely hydration, the symptoms of infant fontanel collapse will slowly improve. There may be other reasons for the sunken fontanel, it is recommended to go to the hospital in time for relevant examinations, to clarify the cause of the disease and then actively treat the symptoms.