The main purpose of this trial is to investigate if any of three different doses of cat hair immunotherapy is safe for treatment of cat allergic patients.

Inclusion Criteria:

• A history of rhinoconjunctivitis on exposure to cats
• Positive Skin Prick Test response (wheal diameter at least 3 mm larger than the negative control
• Positive specific IgE against Fel d1 (at least IgE Class 2)
• Minimum qualifying rhinoconjunctivitis symptom score during EEC exposure at Visit 2

Exclusion Criteria:

• Uncontrolled asthma within the past 12 months, or asthma requiring regular use of inhaled corticosteroids
• FEV1 less than 80% of predicted
• Subjects who suffer from significant seasonal allergic rhinoconjunctivitis, and cannot complete the clinical trial outside the local pollen season, or who have significant allergy to other allergens (e.g. other animals or house dust mites) that cannot be avoided during the trial period
• Subjects who cannot tolerate baseline challenge in the Environmental Exposure Chamber
• History of anaphylaxis with cardio/respiratory symptoms
• A medical history of severe drug or food allergy with symptoms such as difficulty breathing, swelling of the face or a feeling of severe dizziness or increased heart rate
• Chronic urticaria
• History of severe cardiac disease
• Treatment with immunosuppressives, anti-IgE monoclonal antibodies, tricyclic antidepressants or MAOIs