Children’s old crying may be related to physiological factors, or may be caused by indigestion, vitamin D deficiency rickets and other reasons. 1. Physiological factors: If it is a smaller baby, it may be due to the environment temperature is too high, too low, stomach hunger and other reasons caused by the old crying. If it is a bigger child, it may be caused by localized bruises or sprains on the limbs during play, causing the old crying. 2. Indigestion: If the baby is breastfeeding, it may be due to improper feeding, resulting in indigestion, causing the old crying. If it is an older child, it may be due to a one-time large amount of food containing high protein, or cold food, resulting in indigestion, caused by the old crying. 3. Vitamin D deficiency rickets: common in a few months of infants, due to a serious lack of vitamin D in the body, resulting in increased nerve excitability, there may be a phenomenon of old crying, may also be accompanied by restless sleep, head sweating and other symptoms. Children always crying, may also be caused by other reasons, if the symptoms are serious, should seek medical treatment as soon as possible, after diagnosis of the cause, give targeted treatment.