Gold salts have long been used in the treatment of rheumatoid arthritis. However, the basis for their therapeutic immune-modulating properties has never been satisfactorily explained. Furthermore, treatments are often marred by the development of adverse immune reactions such as hypersensitivity and even exacerbation of autoimmunity. We would like to propose a hypothesis to explain the basis for both the beneficial and adverse immune-modulating effects of gold in the treatment of rheumatoid arthritis. If accepted, this hypothesis will allow for the development of safer and more effective treatments with gold salts. The principle underlying this hypothesis also has broader implications for how immune hypersensitivity and tolerance are perceived.