Why do I need both primary and secondary antibodies in western blot?

Western Blot needs both primary and secondary antibodies to successfully detect the antigen of interest. Western Blot involves probing the blocked membrane with a primary antibody that binds to a specific antigen or epitope on a group of antigens. In most cases, the primary antibody that binds to the antigen of interest in a western blot assay cannot be detected directly. Using tagged secondary antibodies that bind to the primary antibody helps to detect the target antigen via indirect detection.