  We motivate the use of dressed charges by arguing that such objects are
needed to describe, e.g., constituent quarks and, in general, physical charged
states in gauge theories. We give a short introduction to dressings in both QED
and QCD. We put special emphasis on the infra-red properties of a moving
dressed charge. To be more precise, we demonstrate that the one loop propagator
of a relativistic dressed charge can be renormalized in the mass shell scheme
with no infra-red divergence showing up.
