The primary objective of the trial is to evaluate the dose-response relationship with regards to change in immunological parameters and safety for SLITone ULTRA house dust mite mix in adult subjects with moderate to severe HDM allergic rhinitis.

Inclusion Criteria:

• Aged 18 or older
• Moderate to severe persistent HDM allergic rhinitis with or without asthma
• Moderate to severe HDM allergic rhinitis symptoms during a baseline period
• Positive skin prick test response (wheal diameter ≥ 3 mm)
• Positive specific IgE ≥ IgE Class 2, ≥ 0.70 kU/l)

Exclusion Criteria:

• Previous treatment with immunotherapy with House dust mite immunotherapy
• Ongoing treatment with any allergen specific immunotherapy product
• Reduced lung function
• Clinical history of uncontrolled asthma
• Inflammatory conditions in the oral cavity with severe symptoms
• History of anaphylaxis with cardiorespiratory symptoms
• History of recurrent generalised urticaria
• A history of drug induced facial angioedema or hereditary angiooedema
• Any clinically relevant chronic disease (≥3 months duration)
• Systemic disease affecting the immune system
• Immunosuppressive treatment
• Currently treated with tricyclic antidepressants; catecholamine-Methyltransferase inhibitors and mono amine oxidase inhibitors