When an eight-month-old baby has a constant runny nose, it is usually considered that the baby has rhinitis and sinusitis, which is the main clinical diagnosis of allergic rhinitis. Treatment should look for allergens and avoid repeated exposure or intake of allergens for the symptoms of runny nose to disappear completely. During the runny nose, you can give your baby anti-allergy medications, such as cetirizine hydrochloride or loratadine, etc.; at the same time, you can buy saline nasal spray to clean nasal secretions. Babies with rhinitis and sinusitis are susceptible to respiratory viral or bacterial infections when their resistance decreases, causing aggravation of symptoms, so they should also pay attention to improving their immunity, ventilating the room and washing their hands regularly to prevent them from catching cold and aggravating the symptoms of runny nose. If there are factors of viral or bacterial infections, they also need to be treated and handled accordingly.