  We provide an effective Lagrangian analysis of contact non-standard
interactions of neutrinos with electrons, which can be effectively mediated by
extra particles, and examine the associated experimental limits. At present,
such interactions are strongly constrained only for $\nu_\mu$: the bounds are
loose for $\nu_e$ and absent for $\nu_\tau$. We emphasize the unique role
played by the reaction $e^+e^-\to \nu \bar{\nu}\gamma$ in providing direct
constraints on such non-standard interactions.
