So far we have considered the salt-free case, where no extra screening is present but just the one from the released counterions and, therefore, the electrostatic interactions are the strongest. Despite its theoretical interest, this is a rather instructive case and of limited application. Although experi- mentally it is possible to reproduce to a well approximation the salt-free limit by means of, for instance, ion-exchange resines, in most of the cases extra ions from salt dissociation are present. Moreover, the role of the extra added salt results fundamental for biomedical and drug-delivery applications. Therefore, we explore next the effect of salt in swelling and the performance of the methods under these conditions.