Newborns with constant tearing in one eye may be related to inverted eyelashes, or it may be caused by newborns with dacryocystitis, tear duct obstruction and other reasons. 1. Inverted eyelashes: If a newborn has inverted eyelashes in one eye, due to the growth of eyelashes in the direction of the eyeball, it will form an irritation to the eyeball, and it may show that one eye is always tearing, and may also be accompanied by redness of the eye, eye pain and other symptoms. 2. Neonatal dacryocystitis: It is usually caused by congenital developmental disorders of the lacrimal duct in newborns, which leads to the secretion of the lacrimal sac and tear fluid can not be discharged, resulting in secondary infection of the nasolacrimal duct. Due to inflammation stimulation, it may show the symptom of one eye always tearing, and may be accompanied by pus overflow, lacrimal sac mass and other manifestations. 3. Lacrimal duct obstruction: If a newborn baby has an obstruction of the lacrimal duct in one eye, resulting in the inability to discharge tears, it may show one eye always tearing, and may be accompanied by pain, purulent discharge and other manifestations. It is recommended to consult a doctor as soon as possible to diagnose the cause of the problem and then treat and regulate the condition under the doctor’s guidance.