Grass Observational Study

Inclusion Criteria: * History of moderate to severe rhinoconjunctivitis consistent with allergy to grass for at least 2 years. * Forced Expiratory Volume in 1 Second (FEV1) of at least 70% of predicted value or personal best if available at the Screening Visit. * Perennial Rye grass or Timothy grass-specific IgE ≥ 0.35 kU/L as measured by ImmunoCAP®. * Positive skin prick test to Perennial Rye grass or Timothy grass allergen Exclusion Criteria: * Positive skin prick test ≥ 5 mm to any confounding, co-existing seasonal allergens likely to be present during the pre-season baseline and grass pollen period. * Medical records of symptomatic perennial allergic rhinitis and/or asthma or a positive skin test ≥ 5 mm due to a perennial allergen to which the subject is regularly exposed (moulds, dust mites, cockroaches, and animal dander) and which cannot be avoided during the course of the study. * Previous immunotherapy treatment with any grass allergen for more than 1 month within 5 years prior to screening. * Subjects who had been treated with any non-grass licensed allergen immunotherapy extracts or non-grass investigational immunotherapy for more than 1 month within 1 year.