A first or second polypeptide for use in a method of treating or preventing a disorder by tolerization, wherein said method comprises administration of the first and second polypeptide； and wherein both first and second polypeptides: i) are of 7 to 30 amino acids in length； ii) comprise at least one MHC Class II-binding T cell epitope； and iii) are a fragment of a protein allergen or a homologous variant of said fragment； wherein said first polypeptide induces the release of an amount of IL-10 that is greater than the amount of IL-10 released in response to the whole protein allergen from which the first polypeptide derives； wherein said disorder is characterized by an inappropriate immune response to the protein allergen from which the second polypeptide derives.
