Saline is made up of sodium chloride and water. Hypertonic saline and isotonic saline have different concentrations, serve different purposes and are used in different ways. The concentration of hypertonic saline and isotonic saline is different, the osmotic pressure of hypertonic saline is higher than the osmotic pressure of human blood and tissue fluids, and the concentration of isotonic saline is 0.9%, which is composed of water and sodium chloride, the same as the osmotic pressure of the human body. Hypertonic saline and isotonic saline have different roles, hypertonic saline is mainly used for wound swelling, but also can correct the internal environment of patients with hypotonic dehydration, but also can be used with mannitol to reduce cerebral edema. Isotonic saline, commonly used as a solvent for many medications, helps rehydrate the body. Hypertonic saline and isotonic saline are used differently; hypertonic saline is used for short-term use usually for 5 to 7 days when the nasal passages are blocked, while isotonic saline can be used for a long period of time to moisten and clean the nasal mucosa. The use of medication should be under the supervision of a doctor.