4-year-old runny nose for more than half a month may be pediatric allergic rhinitis, common cold and other conditions, patients need to follow the doctor’s instructions for general measures, medication. 1. Pediatric allergic rhinitis: usually patients need to try to avoid contact with known allergens, such as pollen, feathers, etc., and usually need to pay more attention to is indoor ventilation, regular cleaning bed sheets, covers and other household items. If the patient’s symptoms are more serious, you need to use saline to rinse the nasal cavity under the guidance of a doctor, and follow the doctor’s instructions to use antihistamines such as cetirizine hydrochloride drops. At the same time, the patient can also be combined with the use of montelukast and other leukotriene receptor antagonists, mometasone furoate and other nasal glucocorticoid therapy. 2. Common cold: Usually, patients need to pay attention to rest, drink more water, and maintain nasal, pharyngeal and oral hygiene. When the symptoms are severe, decongestants such as ephedrine nasal drops can be used to relieve the symptoms. Patients can also use pediatric aminophenol xuanamin granules and other cold medicines to treat. It is recommended that a 4-year-old baby with a runny nose for more than half a month should consult a doctor in a timely manner, improve the relevant examinations to clarify the diagnosis, and follow the doctor’s instructions to take reasonable treatment measures.