Some people like to breathe with their mouths open when they sleep, which is harmful to their health. It should be corrected. Don Sun Simiao's "A thousand dollars is essential, and the Taoist forest nourishes qi" says: When you rest at dusk, evil will quench your thirst and lose blood. It requires people to close their mouths and breathe through their noses when lying on the top of the bed. Breathing with your mouth open can cause some diseases. It is very scientific to say that it is only air to breathe with your mouth open when dust is easy to inhale. Breathing through the airway and waking up to and from the mouth and pharynx will make people thirsty and even cause many respiratory diseases. Some medical staff take the danger of breathing with their mouths open at night more seriously. In the book The Secret of Longevity, Shi, a famous health preserving family in the early Qing Dynasty, said: When sleeping at night, you often practice keeping your mouth shut to nourish your vitality. When you open your mouth, you lose a person's vitality, and evil will enter your mouth and bleed. Anyone who lies with his mouth open at night will feel sick when his teeth touch. Shi's own clinical experience warns people that sleeping at night and getting angry with one's mouth can easily lead to the syndrome of dull complexion, dizziness, cold pulse in limbs, deficiency of qi and blood, and premature tooth loss. People should attach great importance to it. Some people are forced to open their mouths to breathe because of nasal polyps or rhinitis. If this happens, you should go to the hospital for examination and treatment in time.