  In a class of low-energy supersymmetry models the photino is a natural dark
matter candidate. We investigate the effects of post-freeze-out photino
annihilations which can generate electromognetic cascades and lead to
photo-destruction of $^4$He and subsequent overproduction of D and $^3$He. We
also generalize our analysis to a generic dark matter component whose relic
abundance is {\it not} determined by the cross section of the
self-annihilations giving rise to electromagnetic showers.
