  The relativistic generalization of the broken continuity equation that
describes spin currents is exploited in general material media. The field
theoretical techniques for the usual U(1) gauge theory with fermions in
material media is employed. The spin current equations are obtained from the
study of the symmetries of electrodynamics in material media. Moreover, we
obtain the conditions that constrain the spin current to be conserved. One of
the novel results is that the analogue spin current for the photon can be also
defined. In the latter case, the conditions are useful constraints on the
fields and the properties of the media.
