Clear nasal discharge is a symptom of a cold caused by a viral infection due to catching cold. The viral infection can lead to the swelling of the nasal mucosa, increased secretions, and mucosal edema, hence the occurrence of clear nasal discharge, which is a typical early sign of a cold. During this period, it is necessary to maintain indoor air temperature and humidity, avoid eating highly irritating foods, and avoid exposure to smoke, dust, and other irritating chemical gases. Drink plenty of water, and consider taking medications known to affect glandular secretion, as well as vitamin supplements to promote the repair of tissue mucosa.