Severe nasal blockage that prevents breathing can be caused by common cold, nasal foreign body, allergic rhinitis and deviated nasal septum, etc. If necessary, you need to go to the hospital for consultation and treatment. 1. Common cold: Due to the congestion of nasal capillaries, patients with common cold may have symptoms of nasal congestion, in addition, common cold will also have sneezing, runny nose, sore throat and other symptoms. 2. Nasal foreign body: this cause can lead to this symptom, often for foreign body stimulation of nasal mucosa edema and secretion increase caused by the disease. 3. Allergic rhinitis: If the nasal congestion is caused by contact with allergens and accompanied by paroxysmal sneezing, itchy nose and other symptoms, then it is suffering from allergic rhinitis. 4. Deviated septum: Nasal congestion is the most common symptom of deviated septum, in addition to headache, nosebleed, loss of smell and other symptoms. If you have unexplained nasal congestion and can’t breathe, it may be caused by nasal and sinus tumors, etc. It is recommended to go to the hospital in time to get a clear diagnosis and take the right treatment under the guidance of the doctor.