One side of nasal bleeding can occur in various parts of the nasal cavity: 1. The most common cause is because of digging the nose or handling nasal hair, which causes the mucous membrane in the front part of the nasal cavity to erode, resulting in bleeding because the blood vessels lose the protection of the mucous membrane. The most common cases of nasal bleeding are first treated symptomatically by not digging the nose again, and the surface can be coated with Bactrim ointment or erythromycin ointment. 2. The more common causes are nasal bleeding due to poor blood pressure control in patients with hypertension. 3. There are also blood disorders, such as leukemia and allergic purpura, which cause nasal bleeding due to abnormalities in the clotting mechanism. 4. Diseases and inflammation, such as sinusitis, deviated septum, atrophic rhinitis, nasal foreign body, etc., may lead to nasal bleeding.