Under normal circumstances, after tear secretion, except for part of the tears being evaporated into the air, the vast majority of the tears collect at the corner of the eye and enter the nasal cavity through the upper and lower tear dots, tear ducts, tear sacs and nasolacrimal ducts. If the secretion of tears is more or if any part of the tear drainage channel is blocked, the production and discharge of tears loses its dynamic balance, which will cause tearing. The normal tear duct opens at the lower nasolacrimal duct when the baby is 8 months old in the embryo; by the time the tear duct is developed at birth, the tear duct is completely open. Therefore, the vast majority of babies are born with large, clear, bright eyes and normal tear drainage. Only about 6% of full-term infants have incomplete or abnormal lacrimal development during embryonic development, resulting in congenital lacrimal disease, the most common of which is the lower end of the nasolacrimal duct not yet fully developed, i.e., “congenital nasolacrimal duct obstruction”, which prevents tears from flowing into the nasal cavity and causes tear overflow. When the tears and tear sac secretion storage, the baby will have a lot of mucous secretion overflow, and when the bacteria with the tear flow into the tear duct and in which the storage and reproduction, will form a dacryocystitis, the baby will overflow tears and a lot of purulent secretion storage and overflow.