New parents often encounter this situation a few weeks after the birth of the baby: the original good child suddenly screamed loudly, arms and legs stiffened, arching back and fist, crying, that kind of scene makes people caught off guard! What’s wrong with the baby? It is a “symptom” rather than a diagnosis, the cause of which is unknown, and is usually characterized by “explosive, unsettling crying. There are usually 3 rules: 1) it lasts at least 3 hours in a day, at least 3 days a week, and at least 3 weeks; 2) it occurs within 3 weeks after birth; 3) it rarely lasts more than 3 months; 4) it occurs in healthy babies. The most common causes are caused by gastroesophageal reflux and food or formula allergies.