The purpose of the study is to evaluate the more efficient dose for the treatment of rhinitis/rhinoconjunctivitis against grass pollen allergy

Double blind placebo-controlled study. The subjects will receive medication during 4 months.

Inclusion Criteria:

• Written informed consent
• Positive suggestive clinical history of intermittent or persistent moderate to severe rhinitis /rhinoconjunctivitis, with or without moderate asthma, due to grass pollen allergy
• Subjects with a positive skin prick-test (wheal sixe >6 mm diameter) Specific immunoglobulin E (IgE, CAP >3) to grass pollen
• Age between 14 and 65 years
• Both genders
• Subjects capable of giving informed consent
• Subjects capable of complying with the dosing regimen
• Subjects that have not received immunotherapy in the last 5 years
• Subjects presenting sensitization to another aeroallergens and or mites, cats or dogs, but that is considered clinically not relevant or no clinical interference with the nasal provocation test.

Exclusion Criteria:

• Subjects outside of the age range.
• Subjects who have previously received immunotherapy for the treatment of the allergic rhinitis/rhinoconjunctivitis due to grass pollen and other allergens in the last 5 years.
• Subjects that immunotherapy may be an absolute contraindication according to the criteria of the immunotherapy Committee of the Spanish society of Allergy and Clinical Immunology, and of the European Allergy and Clinical Immunology Immunotherapy Subcommittee may also include.
• Subjects with important symptoms of rhinoconjunctivitis /bronchial asthma in which the suspension of the systemic antihistamine treatment is contraindicated.
• Subjects with persistent severe or not controlled asthma , with a forced expiratory volume (FEV) < 70 respect to the reference value in spite of the appropriate pharmacological treatment at the time of the inclusion in the trial.
• Subjects that have required oral corticosteroids in the 12 weeks previous to the inclusion in the trial.
• Subjects that have previously submitted a serious secondary reaction during the skin prick test
• Subjects in treatment with beta blockers.
• Unstable subjects from the clinical point of view (respiratory infection, febrile, acute urticaria, etc.) at the time of the inclusion in the clinical trial
• Subject with chronic urticaria in the last 2 years or hereditary angioedema.
• Subjects that have some pathology (hyperthyroidism, hypertension, heart disease, etc.) is contraindicated.
• Subjects with any other disease not associated with the rhinitis/rhinoconjunctivitis, but of potential severity and that could interfere with treatment and follow-up (epilepsy, psychomotor deterioration, diabetes, malformations, multi-operated, kidney diseases,...).
• Subjects with autoimmune disease (lupus, thyroiditis, etc.), tumor or with diagnosis of immunodeficiency diseases.
• Subject whose status prevents him from providing cooperation and or which present severe psychiatric disorders.
• Subject with known allergy to other components of the vaccine different from pollen of grasses.
• Subjects with lower airway diseases other than asthma such as emphysema or bronchiectasis.
• Direct investigator's relatives.
• Pregnant or women at risk of pregnancy and breastfeeding women.