Race and ethnicity are well-established epidemiological categories that relate to the patients' risk of exposure and their susceptibility/resistance to disease. However, this association creates the notion that factors other than a personal identity need not be held responsible for patients' health problems. This work deconstructs the notion of race and ethnicity as risk factors for immigrant ill health, which is prevalent in current medical research and practice, by tracing its roots in Canadian history. The understanding that medical knowledge is subject to diverse historical, social, cultural and political influences can change the way health professionals perceive their patients as a health threat.