ATIBAR - Efficacy and Safety of Two Doses of AllerT in Patients Allergic to Birch Pollen

Inclusion Criteria: * Adult subjects 18 to 65 yrs old, male or female * moderate to severe allergic Rhinitis/Rhinoconjunctivitis to birch pollen during the two preceding birch pollen seasons * positive Skin Prick Test (SPT) to birch pollen extract * positive specific IgE CAP to Bet v1. Exclusion Criteria: * persistent non-controlled asthma (Forced Expiratory Volume, FEV1 \< 85% of predicted), * previous specific immunotherapy (SIT) to tree pollens, * previous SIT to any allergen within 5 years, * previous history of severe anaphylactic reaction, * perennial allergic Rhinitis/Rhinoconjunctivitis, * other disorder possibly influencing the trial outcomes, * pregnancy, * any severely debilitating disease, * primary or secondary immunodeficiency or treatment with immunosuppressor drugs within one month prior to randomization (oral steroids, other immunosuppressors).