Polypeptides which may be used for preventing or treating allergy to moulds of the Cladosporium and/or Alternaria genus, have up to 30 amino acids in length and comprise: (I) the amino acid sequence: (a) GGYKAAVRPTMLE (SEQ ID NO: 35 Cla35), (b) AE V YQKLK SLTKK (SEQ ID NO: 31 Cla16), (c) VAITYASRAQGAE (SEQ ID NO: 32 Cla25), (d) GHHFKERGT-GSLVIT (SEQ ID NO: 33 Cla26), or (e) ANYTQTKTVSIRL (SEQ ID NO: 34 Cla29) or (II) a T cell epitope-containing variant sequence which is a said amino acid sequence (I) having up to six amino acid modifications, each of which is independently a deletion, substitution or insertion.