The health of exiles—whether immigrants, refugees, asylum seekers, or undocumented foreigners—is generally better upon arrival than that of nationals in so-called host countries, but it deteriorates rapidly in those countries, due not only to difficulties in accessing healthcare but also, and above all, to the treatment they receive from the society where they had hoped to build a new life. Tracing back over a century of history, Didier Fassin analyzes how what has been termed “migrant health” has been and is perceived through hygienist, tropicalist, differentialist, and epidemiological approaches. He questions this segmentation of a particular field of health, as if there were a singularity to “migrants” justifying their study as a specific reality. On the contrary, he shows that their health depends largely on the conditions in which they are forced to live and work.