4 and a half year old children often run a clear nose, may be allergic rhinitis, acute rhinitis, etc. caused. 1. Allergic rhinitis: allergy-related, especially children belong to the allergic body, encounter seasonal changes, pollen, dust, food, drugs and other allergens repeated quality stimulation, often appear to flow clear, sneezing symptoms, the general use of anti-allergy drugs, such as loratadine, etc. can be relieved. 2. Acute rhinitis: this disease is caused by viral infection of the nasal mucosa acute inflammation, belongs to the upper respiratory tract infection, seasonal changes susceptible. It can be characterized by dryness, itchiness, burning sensation, sneezing, nasal congestion, runny nose, loss of smell and other symptoms. Treatment can be given to saline nasal spray rinse nasal cavity, antihistamine drugs cetirizine anti-allergy treatment. Four and a half year old children often run clear nose, there may be other causes, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment, the above medication as prescribed by the doctor.