Semen has no significant benefit to the female vagina. Semen is mainly composed of two parts, sperm and seminal plasma, with sperm accounting for about 5% and the remainder being seminal plasma. The main role of sperm is to conceive and reproduce offspring. And seminal plasma contains a large amount of water, fructose, protein and peptides, in addition to more sugars such as glucose, enzymes, inorganic salts and organic small molecules. Although seminal plasma contains enzymes and the rest of its components are closer to those of blood plasma, it still does not have a bactericidal effect. Because it does not contain the cells in plasma, i.e. neutrophils and macrophages, these components do not have a bactericidal effect and have no significant benefit to the female vagina. On the contrary, if a man has a disease, such as hepatitis B, AIDS or syphilis, his semen may also carry disease-causing microorganisms and viruses that can be transmitted to others through sexual intercourse.