Repetitive streamer discharges due to high-frequency AC voltage can ignite H2/air mixtures and are the focus of research concerning the explosion protection of electrical apparatuses. The ignition process is not understood in detail. In streamer discharges, a non-equilibrium plasma occurs leading to the formation of chemically active radicals, such as atomic oxygen and atomic hydrogen as well as hydroxyl. The influence of the radical build up during repetitive streamer discharges on the ignition process is examined. Using detailed chemical kinetics describing the discharge phase and its afterglow, the ignition of H2/air mixtures is studied. The influence of the reduced electric field and the electron density on the ignition is examined numerically.