QED radiative corrections for parton distributions

I discuss radiative corrections due to the emision of photons from quarks which contribute to deep inelastic lepton-nucleon scattering as well as to pp collisions at high energies. These corrections are dominated by quark-mass singularities which have to be absorbed into the parton distribution functions. Observable effects appear as a modification of the Q² dependence of the distribution functions. Numerical results indicate, however, that these QED corrections are negligible except at extremely large Q² and large x. Therefore it is safe to neglect the single and multiple photon effects in pp scattering at CERN LHC energies.