The present invention provides a nucleic acid sequences coding for the ryegrass pollen allergens Lol pIa and Lol pIb, purified Lol pIa and Lol pIb protein and fragments thereof, methods of producing recombinant Lol pIa and Lol pIb or at least one fragment thereof or derivative or homologue thereof, and methods of using the nucleic acid sequences, proteins and peptides of the invention.