Allergic diseases represent a major health issue worldwide and epidemiological studies in Melbourne, Australia, have reported a high prevalence of rhinitis (hayfever) and atopy (genetic tendency to make allergy antibody) in Asian and Caucasian subjects. Mainstay treatment of allergic rhinitis is allergen avoidance and pharmacotherapy for symptom relief. Allergen immunotherapy offers the advantages of specific treatment with long lasting efficacy, and can modify the course of disease. However, use of this treatment is restricted by the high risk of adverse events especially in asthmatics. Other, better tolerated, routes of allergen administration than the current conventional subcutaneous route (SCIT) have been investigated including the sublingual route (SLIT) and recently sublingual tablets for pollen allergy immunotherapy became available. The tablets are safe and easy to use and contain pollen extracts from 5 of the most common allergy-causing European grasses but include ryegrass (Lolium perenne), the major seasonal pollen for allergy in Melbourne and south-eastern Australia. The immunological mechanisms of sublingual immunotherapy are not fully understood. The investigators propose conducting a longitudinal open label study to investigate the immunological changes that occur with the 5 grass pollen sublingual immunotherapy tablet (Oralair®) in a cohort of Chinese and non-Chinese background subjects. The investigators will investigate the induction of relevant T cell regulatory immune mechanisms and changes in serum allergen-specific immunoglobulin (Ig) E and IgG4. Immunoregulatory cytokine synthesis and T cell phenotype (Bio-plex and flow cytometry) will be examined. This project will provide important fundamental knowledge on which to inform decisions for the greater application of this treatment for subjects with moderate and severe allergic rhinitis.