This is a single center open study designed to determine the concentration of airborne birch pollen inducing an allergic conjunctivitis response in individuals allergic to birch pollen, during allergen exposures in the Alyatec environmental exposure chamber (EEC).

Inclusion Criteria:

• Subjects having signed the informed consent
• Subjects affiliated to a social security scheme
• Subjects with birch pollen rhinitis and conjunctivitis with:
• A history of rhinoconjunctivitis for at least the last 2 consecutive pollen seasons.
• A positive skin prick-test to birch (wheal diameter >6 mm compared to the negative control),
• Specific immunoglobulin E (IgE) for birch> 0.1 kIU/l
• Women of childbearing potential must have a negative pregnancy test during the entire study period with an effective means of contraception: oral contraceptives, intrauterine device, condom with spermicide for at least one month before inclusion in the study and for the duration of the study. At each study visit and each exposure on D1, a urine pregnancy test will be performed.
• A positive conjunctival provocation test to birch during the screening visit at a dilution of 100IR/ml maximum

Exclusion Criteria:

• Known asthmatic subjects allergic to birch pollen
• Use of oral corticosteroids in the 4 weeks preceding inclusion in the study
• Use of biotherapy in the 4 months preceding inclusion in the study
• Desensitization to birch pollen in the last 5 years
• Uncontrolled chronic pathologies (hypertension, cardiac, respiratory, renal pathology).
• Active autoimmune disease
• Uncontrolled systemic hypertension
• Subjects who participated in another clinical study in the three months prior to inclusion
• Pregnancy and breast feeding
• Inability to understand and act upon the information provided