One nostril is always airless when sleeping, which may be caused by chronic simple rhinitis, nasal polyps, deviated septum and so on. 1. Chronic simple rhinitis: there will be intermittent or alternating nasal congestion, alleviated during the day or after activities, aggravated by sedentary at night, resulting in sleeping always a nostril airless. 2. Nasal polyps: Nasal mucosal polyps may occur unilaterally, which may also cause one nostril to be out of breath when sleeping. 3. Deviated nasal septum: It refers to the abnormal structure of the bone and cartilage of the nasal septum, such as the side of the deviation that leads to poor ventilation of the nasal cavity, you can always sleep with one nostril not ventilated. Sleeping always a nostril, there may be other reasons, need to go to the hospital in time to check, follow the doctor’s instructions for treatment.