Antigens do not necessarily have to be foreign substances; some components of your own body can also become antigens. Antigens are substances that can cause the body to produce antibodies and be able to bind antibodies or sensitize lymphocytes for an immune response, and can be classified as exogenous antigens, endogenous antigens, and synthetic antigens. Exogenous components generally include viruses, bacteria, fungi, mycoplasma, chlamydia, parasites, pollen, etc., the body’s eye crystal proteins, sperm cells, thyroglobulin, serum proteins and other material components may also become antigens, and synthetic antigens are mainly the formation of vaccines after inactivation and attenuation treatment. Therefore, antigens should be categorized according to different sources, and when discomfort occurs in the body, it is important to go to the hospital for examination in a timely manner.