4-month-old babies crying in fear may be caused by hunger, environmental discomfort, gastrointestinal discomfort, calcium deficiency and so on. 1. Hunger: If the amount of feeding is insufficient, causing the baby to be in a state of hunger, it may lead to the baby’s crying. 2. Environmental discomfort: If the environment in which the baby sleeps is not quiet or the room temperature is not suitable, it will cause the baby to cry. 3. Gastrointestinal discomfort: If there is frequent bloating and the number of bowel movements increases or decreases, it may be the result of intestinal flora imbalance, intestinal spasms, intestinal gas buildup, indigestion, and other factors that cause babies to cry out in fear. 4. Calcium deficiency: babies should be supplemented with vitamin D after birth to promote the absorption of calcium and phosphorus, otherwise it is easy to be low in calcium, and babies will have frightened crying and excessive sweating. If it persists for a long time, it is recommended to go to the regular hospital in a timely manner, under the diagnosis of the doctor, according to the patient’s specific condition performance, to take targeted treatment.