Inclusion Criteria:

• 18 to 65 years of age
• Mild to moderate seasonal allergic rhinoconjunctivitis due to sensitization against grass pollen as evident from history (≥ 2 years), and positive nasal provocation test (NPT) and positive skin prick test (SPT, wheal ≥ 3mm larger than diluent) to grass pollen extract
• Female participants must meet one of the following criteria:

No reproductive potential due to menopause (one year without menses, in case of doubts serum FSH will be determined and must be >40 U/mL), hysterectomy, bilateral oophorectomy, or tubal ligation. Patient agrees to consistently practice an effective and accepted method of contraception throughout the duration of the study and for 1 additional months after the last immunization (hormone-based, or intrauterine device, or double barrier contraception, i.e. condom + diaphragm, condom or diaphragm + spermicidal gel or foam)

• Written informed consent
• Patient is willing and able to comply with all trial requirements

Exclusion Criteria:

• Additional allergies (seasonal or perennial) of which the symptoms overlap temporally with the screening and treatment period
• Contraindication to Allergen Preparation
• Contraindication for Nasal Provocation Test
• Contraindication for Skin Prick Test
• Actual significant obstructive pulmonary disorder (FEV1< 70%)
• Pharmacological treatment that could affect allergic sensitivity during the trial
• Presence or history of significant cardiovascular, renal, pulmonary, endocrine, autoimmune, neurological, and psychiatric disease as judged by the investigator
• Serum test positive for HIV, HBV, or HCV
• Current diagnosis or history of malignancy; presence of suspicious lymphadenopathy or splenomegaly on physical examination
• Pregnancy or lactation
• Blood donation within 30 days before enrolment
• History of abuse of alcohol or other recreational drugs
• Specific immunotherapy against pollen allergy within the last two years
• Intake of an investigational drug within three month before enrolment
• Intake of contraindicated medicaments for SIT as Betablockers, ACE/ATII Inhibitors