A 3-month-old baby with a runny nose is commonly seen in two situations: i. Allergic rhinitis. Allergic rhinitis is commonly seen in babies in the early morning, when they are exposed to cold air, smell special odors, etc.. Often accompanied by sneezing, clear nasal water, can be treated with nasal sprays, commonly used budesonide nasal spray. Second, upper respiratory tract infection, you should let the pediatrician confirm the diagnosis, often you can see redness and swelling in the throat, the child may have fever, sneezing, etc., you should follow the upper respiratory tract infection for treatment, oral Ai Chang is more effective. Babies with yellow, pusy nasal discharge are usually infected with bacteria in the nose and should be treated with appropriate antibacterial medication according to the infected bacteria.