This work reports a nuclear magnetic resonance (NMR) study of both hydrogen and deuterium on two different kinds of ferrofluids. One of them is a colloidal suspension of surfacted magnetic grains dispersed in a mixture of light and heavy water. The second one is an ionic ferrofluid composed by positively charged magnetic grains of Co-Fe2O4 dispersed in the same solution of water. A model of the local magnetic field distribution in the interstitial (bulk) water is worked out in order to account for the broadening of the NMR spectra observed in both samples.