In this talk, I show that dark matter annihilation around the time of recombination can lead to growing ionization perturbations, that track the linear collapse of matter overdensities. This amplifies small scale cosmological perturbations to the free electron density by a significant amount compared to the usual acoustic oscillations. Electron density perturbations distort the CMB, inducing secondary non-gaussianity, offering a means of detection by Planck and other experiments. I will present a novel analytic calculation of CMB non-gaussianity from recombination, providing a clear identification of the relevant physical processes. I will show that, even though electron perturbations can be markedly boosted compared with the standard model prediction, the effect of dark matter annihilation in the CMB bispectrum will be difficult to detect.