One side of the nostrils flow yellow water with odor, consider and acute and chronic sinusitis, unilateral maxillary sinus cyst and other factors related. 1. Acute sinusitis: acute sinusitis, may be secondary to acute rhinitis. It is an inflammation or purulent inflammation of the mucous membrane of the sinuses, which leads to nasal congestion, headache, and purulent nasal discharge. 2. Chronic sinusitis: the occurrence of chronic sinusitis is more complicated, and it is considered to be related to environmental pollution, climate change, and lesions of neighboring organs, which leads to chronic purulent inflammation of the sinuses, and one side of the patient’s nostrils may have yellowish water and bad smell. 3. Unilateral maxillary sinus cyst: one side of the nostrils suddenly flowing yellow water and odor, can also be considered with a unilateral maxillary sinus cyst. Maxillary sinus cysts grow gradually, to a certain extent or infection, rupture of the cyst, yellow water may flow. One side of the nostrils flow yellow water, odor, it is recommended not to deal with their own, can be timely to the hospital ENT department for examination, to identify the cause, under the guidance of the doctor to give medication or through the surgical way of treatment.