  Neutrino interactions with matter play an important role in determining the
nucleosynthesis outcome in explosive astrophysical environments such as
core-collapse supernovae or mergers of compact objects. In this article, we
first discuss our recent work on the importance of studying the time evolution
of collective neutrino oscillations among active flavors in determining their
effects on nucleosynthesis. We then consider the possible active-sterile
neutrino mixing and demonstrate the need of a consistent approach to evolve
neutrino flavor oscillations, matter composition, and the hydrodynamics when
flavor oscillations can happen very deep inside the supernovae.
