Abstract: This invention relates to tolerogenic conjugates, suitable for use in suppressing the formation of reaginic antibodies in a host, of haptenic determinants, in particular the benzylpenicilloyl (BPO) group and 2,4-dinitrophenyl (DNP) group, with water-soluble, nonimmunogenic polymers, i.e. polyvinyl alcohols (PVA). The invention also comprises a method for the preparation of the conjugate and a method of suppressing the formation of these antibodies in a mammal sensitive to penicillin.