A development of number density perturbations of ions and electrons caused by kinetics of helium and hydrogen recombination in the range of cosmological matter density fluctuations is analysed. The equations for relative perturbations of ionization fractions are obtained on the basis of equations for cosmological hydrogen and helium recombination. It is shown that a strong dependence of ionization and recombination rate on density and temperature of plasma in the non-equilibrium regime provides essential deviations of amplitudes of ionization fraction relative perturbations from baryon adiabatic mass density ones. At the moment of the maximal rate of recombination, the amplitudes of relative number density perturbations of electrons and protons at last scattering surface are five times greater than amplitude of relative mass density of baryon matter, for helium ions they are 18 times greater. Such differences of ion number density relative fluctuations and total baryon mass density ones do not result into local temperature fluctuations of the thermal background radiation. The observational manifestation of the ion perturbations in the calculation of the cosmic microwave background anisotropy are studied.