Antigen testing can be done on the nose, or blood, stool, etc., depending on the purpose of the test. Antigens are all substances that can induce an immune response in the body, that is, substances that can be specifically recognized and bound by the antigen receptors on the surface of T lymphocytes or B lymphocytes, activate these two types of cells so that they can proliferate and differentiate, produce immune response products, and specifically bind with the corresponding products both inside and outside the body. Antigen detection can be categorized into heterologous antigen detection, homologous heterodimeric antigen detection, and autoantigen detection. For example, heterologous antigen refers to pathogenic microorganisms, such as bacteria, viruses, mycoplasma and other antigens between different races. Then any body fluids containing viruses, bacteria, and mycoplasma can be used for antigen detection, such as human blood, urine, stool, and respiratory secretions. If the test is for respiratory disease antigens, nose secretions can be tested, as well as secretions from the mouth and throat.