We motivate the use of dressed charges by arguing that such objects ar
e needed to describe, e.g., constituent quarks and, in general, physic
al charged states in gauge theories. We give a short introduction to d
ressings in both QED and QCD. We put special emphasis on the infra-red
properties of a moving dressed charge. To be more precise, we demonst
rate 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.