This pilot study is a Phase IV, single center, placebo-controlled, parallel study design conducted using the Environmental Exposure Unit (EEU). The study will aim to be determine whether there are any benefits from Grastek® for the treatment of birch-pollen induced allergic rhinoconjunctivitis. Grastek® is a Health Canada and FDA approved sublingual immunotherapy (SLIT) for the treatment of grass-pollen induced allergic rhinoconjunctivitis. The EEU provides a closed environment in which participants are exposed to a predetermined, controlled, constant level of airborne pollen. 96 participants will complete this study and will either receive Grastek® or placebo in a 1:1 ratio. The study will consist of a screening visit, a pre-treatment pollen exposure visit, 60 days of treatment with Grastek® or placebo, two treatment visits and a follow-up pollen exposure visit.

Inclusion Criteria:

1. Participant demonstrates understanding and has provided an appropriately signed and dated informed consent.

2. Male or Female, 18 to 65 years of age, at time of the Screening visit.

3. Participant has a history of at least moderate allergic rhinoconjunctivitis due to hypersensitivity to birch pollen for a minimum of 2 years.

4. Participant responds to the birch pollen and timothy grass pollen through a standard skin prick test administered at the Screening visit. A positive test will be defined as a wheal diameter at least 5mm or larger than the negative control (normal saline) wheal. A historical skin-prick test performed within three-hundred sixty-five (365) days or one (1) year at the site will be accepted in lieu of performing a new skin prick test.

5. Participant understands and is willing, able and likely to comply with study procedures and restrictions.

6. Participant, if female, has a negative urine pregnancy test at Visit 1 and is willing to use a medically acceptable form of birth control. Acceptable methods of birth control for this study include:

   • oral, patch, or intra-vaginal hormonal contraceptives
   • Norplant System®
   • Depo-Provera®
   • IUD
   • double barrier method
   • abstinence
   • surgically sterile females (hysterectomy or tubal ligation)
   • > 1 year post-menopausal females
   • same sex partner
   • partner vasectomy (> 3 months)

7. Participant is healthy as determined by pre-study medical history, physical examination and vital signs.

8. Participant is able to read, comprehend, and record all information in English.

9. Participant has a serum specific IgE level to both birch and timothy grass of ≥0.7 ku/L.

Exclusion Criteria:

1. Has significant current nasal or ocular symptoms that the study doctor associates with perennial allergic or non-allergic rhinitis.
2. Female participant who is pregnant or lactating.
3. Has a history of any illness that, in the opinion of the study investigator, might confound the results of the study or poses an additional risk to the participant by their participation in the study. This includes a clinically relevant medical or surgical history or presence of other respiratory disease (exceptions made for asthma and allergic rhinitis as defined in further exclusion criteria), or gastrointestinal, renal, hepatic, hematological, lymphatic, neurological, cardiovascular, psychiatric, musculoskeletal, immunological, dermatological, connective tissue diseases or disorders, or a history of malignancy within the past 5 years, with the exception of non-melanoma skin cancer.
4. Has any significant abnormalities found during physical exam as determined by the investigator.
5. Has a current medical history of significant pulmonary disease and/or active asthma requiring daily drug therapy. Mild, intermittent asthma is permitted (managed with short acting beta-agonist less than 3 times per week). Isolated exercise-induced bronchospasm is also permitted.
6. Has received an investigational drug within the last thirty (30) days.
7. Has had use of immunotherapy containing grass or birch within the last 3 years.
8. Has significant nasal polyps, nasal septal perforation, or nasal tract malformations as noted on physical exam.
9. Administration of adrenaline (epinephrine) is contraindicated (e.g. participants with acute or chronic symptomatic coronary heart disease or concomitant beta-blocker therapy).
10. Is unlikely to cooperate with the requirements of the study including having the ability to communicate with the investigator appropriately.