Tears in the eyes of five-month-old babies may be a normal physiological reaction caused by foreign objects entering the eyes, etc., or it may be caused by pathologic factors such as blockage of the tear ducts, inverted eyelashes and conjunctivitis. 1. Physiological factors: foreign matter such as dust, pollen, etc. into the baby’s eyes, irritating the eyes, resulting in eye discomfort, itching, so that the baby tears. 2. Lacrimal duct obstruction: Lacrimal duct obstruction refers to the obstruction of the lacrimal area due to developmental problems, nasal pathology, etc., which can be manifested as involuntary tearing. 3. Inverted eyelashes: Inverted eyelashes refer to eyelashes that are inverted to the eyeballs, and eyelash friction that irritates the eyeballs can easily lead to tearing in infants. 4. Conjunctivitis: mostly caused by microbial infections or allergies to external stimuli, often manifested as increased eye secretions, tearing and other symptoms. Parents should pay more attention to the daily observation of the baby’s condition, if the baby has serious discomfort, should promptly seek medical treatment, by the doctor for targeted treatment.