Clinical Efficacy and Safety of gpASIT+TM to Treat Seasonal Allergic Rhinoconjunctivitis

Inclusion Criteria: * Age between 18 and 50 years * Subject has given written informed consent * The subjects are in good physical and mental health according to his/her medical history, vital signs, and clinical status * Male or non pregnant, non-lactating female * Female unable to bear children must have documentation of such in the CRF (i.e. tubule ligation, hysterectomy, or post menopausal (defined as a minimum of one year since the last menstrual period)) * Allergy \> 2 years Exclusion Criteria: * Subjects with current immunotherapy or subjects who underwent a previous immunotherapy within the last 2 years * Subjects with perennial asthma * Subjects with a VC \< 80% and FEV1 \< 70% * Subjects requiring controller medication against asthma (bronchodilator nebulised drugs or local or systemic corticosteroids) * Documented evidence of chronic sinusitis (as determined by investigator) * Subjects with a history of hepatic or renal disease * Subjects symptomatic to perennial inhalant allergens * Subject with malignant disease, autoimmune disease * Female subjects who are pregnant, lactating, or of child-bearing potential and not protected from pregnancy by a sufficiently reliable method (OCs, IUD, ...) * Any chronic disease, which may impair the subject's ability to participate in the trial (i.e. severe congestive heart failure, active gastric ulcer, inflammatory bowel disease, uncontrolled diabetes mellitus, etc…) * Subjects requiring beta-blockers medication * Chronic use of concomitant medications that would affect assessment of the effectiveness of the trial medication (e.g. tricyclic antidepressants) * Subject with febrile illness (\> 37.5°C, oral) * A known positive serology for HIV-1/2, HBV or HCV * The subject is immunocompromised by medication or illness, has received a vaccine, corticoids or immunosuppressive medications within 1 month before trial entry * Receipt of blood or a blood derivative in the past 6 months preceding trial entry * Regular consumption of corticoids (oral, topic or nasal) or of anti-histaminic drugs within 4 weeks preceding the trial * Any consumption of corticoids (oral, topic or nasal) or of anti-histaminic drugs within 1 week preceding the trial * Use of long-acting antihistamines * Any condition which could be incompatible with protocol understanding and compliance * Subjects who have forfeited their freedom by administrative or legal award or who are under guardianship * Unreliable subjects including non-compliant subjects, subjects with known alcoholism or drug abuse or with a history of a serious psychiatric disorder as well as subjects unwilling to give informed consent or to abide by the requirements of the protocol * Participation in another clinical trial and/or treatment with an experimental drug within the last 2 years * A history of hypersensitivity to the excipients * Rhinitis medicamentosa, non-specific rhinitis (to food dye, preservative agent…) * Subjects without means of contacting the investigator rapidly in case of emergency, or not able to be contacted rapidly by the investigator