Saliva mainly has moisturizing, cleaning, digestive and protective effects and functions. 1. Moisturizing effect: saliva contains a lot of water, can keep the oral mucosa moist in order to use the oral cavity normal pronunciation and food swallowing. 2. Cleaning effect: oral secretion of saliva on food debris and other substances have a certain scouring cleaning effect, can effectively prevent the accumulation of food debris in the oral cavity, and thus avoid dental caries or periodontal disease. 3. Digestive effect: saliva contains amylase and other digestive enzymes, can be the initial digestion of food, food in the gastrointestinal tract is more effective digestion and absorption. 4. Protective effect: saliva contains lysozyme and other substances, can effectively resist the invasion of external bacteria or infection, thus playing a certain protective effect on the oral cavity.