Children with clear nasal discharge from one nostril are considered to be related to viral colds, allergic rhinitis and cerebrospinal fluid nasal leakage. 1. Viral cold: the disease is mainly related to viral infection, while the decline in immune function, cold and so on are the triggering factors. When a child suffers from viral cold, it may manifest as nasal congestion, sneezing, fever, body weakness, body aches, loss of appetite and other symptoms, and may also manifest as clear nasal discharge from one nostril. 2. Allergic rhinitis: allergic rhinitis is related to genetic factors, inhalation of allergens and other factors. When a child suffers from allergic rhinitis, it may manifest as itchy nose, paroxysmal sneezing, nasal congestion, etc., and may also be accompanied by other symptoms such as clear nasal discharge from one nostril, redness and swelling of the eyes, tightness in the chest and cough. 3. Cerebrospinal fluid leakage: Cerebrospinal fluid leakage can cause some children to have continuous or intermittent discharge of clear watery liquid from the nose, which can be mistaken for clear nasal discharge. Cerebrospinal fluid leakage is mainly related to craniocerebral trauma and medical injury. When a child has clear nasal discharge from one nostril, it should be wiped promptly with a clean tissue. If the child is experiencing other symptoms, seek medical attention.