Isolated nucleic acids encoding allergens of Canis familiaris, Can f I or Can f II, are disclosed. A cDNA encoding a peptide having a Can f I activity and a predicted molecular weight of about 19,200 daltons is also described. A cDNA encoding a peptide having Can f II activity and a predicted molecular weight of about 18,200 daltons is also disclosed. The nucleic acids can be used as probes to detect the presence of Can f I or Can f II nucleic acid in a sample or for the recombinant production of peptides having a Can f I or Can f II activity. Peptides having a Can f I or Can f II activity can be used in compositions suitable for pharmaceutical administration or methods of diagnosing sensitivity to dog dander.