Freund's adjuvant is one of the most commonly used adjuvants in research. It is used as an oil in water emulsion. It is prepared from non metabolizable oils (paraffin oil and mannitol monooleate). If it also contains killed Mycobacterium tuberculosis, it is called a complete Freund's adjuvant. If there are no bacteria, it is an incomplete Freund's adjuvant. Freund's adjuvant was originally developed by Jules Freund in the 1940s, with the design goal of providing sustained release of antigens necessary to stimulate strong and long-lasting immune responses. The main drawback of Freund adjuvant is that it can cause granuloma, inflammation, and damage at the vaccination site. Mycobacterium in complete Freund's bacteria attract macrophages and other cells to the injection site, thereby enhancing the immune response. Therefore, a complete Freund's adjuvant is used for initial injection.