Through our national programmes we meet people in Europe who have fled extreme poverty, violent armies and police forces, conflict areas and disasters. A tiny minority of the children, women and men whom we try to support when we work in their countries end up coming here. After migration journeys which are very often long, dangerous and exhausting, many find themselves without permission to stay in the country, forced into the shadows of our towns and cities. At home, as abroad, Médecins du Monde aims to provide some support and tries to help this population protect what is often the only thing they have left--their health. With this study, we show how undocumented migrants' living conditions are harmful to their health and prevent them from building, or rebuilding, their lives. This is despite the fact that these children, women and men are in particular need of support, given what they have lived through and the migration journeys they have undertaken. Even worse, our own health systems often exclude them from healthcare. Serious health problems receive little medical follow-up, sometimes none at all. Because healthcare sometimes becomes a trap--due to the fact that people are being encouraged or required to report undocumented migrants--we urge that health policy must remain completely independent from immigration policy, respecting the obligations of health and social care.