The purpose of this study is to investigate the safety and tolerability of different doses of sublingual tablets of house dust mite (HDM) allergen extracts in adolescents with house dust mite-associated allergic rhinitis.

Inclusion Criteria:

• Written informed consent from patient and parent(s)/legal representative.
• Male or female patient from 12 to 17 years.
• Diagnosed rhinitis with medical history consistent with HDM-induced allergic rhinitis for at least 1 year before visit 1
• Positive Skin Prick Test to House Dust Mites(HDM)and HDM-specific IgE serum value ≥ 0.7 kUnit/L.
• Concommittant controlled asthma allowed up to GINA 1 or 2 treatment step
• Spirometry with best FEV1 > 80% of predicted FEV1.

Exclusion Criteria:

• Patient with a nasal or oral disease that could interfere with the safety assessments
• Patient has undergone recent nasal surgery
• Patient with asthma receiving therapy consistent with GINA (Global INitiative for Asthama) treatment step 3, 4, or 5.
• Patient with partially controlled or uncontrolled asthma
• Patient with a past or current disease, which as judged by the Investigator, may affect the patient's participation in or the outcome of this study.
• Female patient pregnant or breast-feeding/lactating.
• Female patient of childbearing potential planning a pregnancy during this trial or not using a medically accepted contraceptive method.
• Patient treated with beta-blockers, tricyclic antidepressants or monoamine oxidase inhibitors (MAOIs).
• Patient who received allergy specific immunotherapy for house dust mites for more than 1 month in the 5 years before screening or who is currently receiving immunotherapy with any allergen.
• patient with a history of anaphylaxis
• patient having participated in any clinical study within the 12 weeks before visit 1