Allergic diseases represent a major health issue worldwide. Mainstay treatment 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 sublingual (SLIT). However, the immune parameters of SLIT have not been examined. We propose conducting a randomised, placebo-controlled study of a commercially-available SLIT for house dust mite (HDM) allergy to investigate induction of relevant T cell regulatory immune mechanisms. The first year will be followed by an optional open label extension period. Immunoregulatory cytokine synthesis and T cell phenotype and function (real time PCR and flow cytometry) will be examined. This project will provide important fundamental knowledge on which to base improved and greater application of this potentially curative treatment for allergy. SLIT has the potential advantage of home administration and suitability for patients with asthma who are currently unable to access many of the allergen desensitising regimens.

Inclusion Criteria:

• allergic rhinitis and/or
• mild stable asthma
• house dust mite allergic
• positive HDM-specific IgE as determined by skin prick test (wheal diameter >6 mm to D. pteronyssinus) or CAP-Pharmacia score > 2

Exclusion Criteria:

• Immunodeficiency diseases
• Severe or uncontrolled asthma
• Previous immunotherapy with House dust mite (HDM) extract within the last five years or ongoing immunotherapy with HDM or other allergens
• Continuous oral corticosteroids
• Subjects on treatment with beta-blockers
• Pregnant women