Inclusion Criteria:

• a) Have a known past history of allergic rhinitis including allergy to ragweed pollen.

  b) Able and willing to give informed consent. c) Able and willing to follow all study related instructions. d) Able and willing to make all required visits. e) Aged between 18 and 80 years. f) Willing to avoid prohibited medications (see below). g) Has met at least one of the endpoints to allergen challenge at Visit 1

  1. Total symptom score of at least 6 OR

  2. ≥ 30% reduction in nasal volume in at least one side of the nose as measured by acoustic rhinometry AND total symptom score of at least 4. h) Has met endpoint to allergen challenge at Visit 2: Total symptom score of at least 4 from a possible total of 12.

     Exclusion Criteria:

• a) Patients with known exaggerated immuogenicity responses including severe asthma or peanut allergy. b) Patients with known allergy to ticks or severe reaction to arthropod venom (e.g. bee or wasp venom). c) Patients with known chronic sinusitis, deviated nasal septum or nasal polyposis.

  d) Patients having a total Baseline symptom score of >4 at Visit 1 (ie before the first nasal washout). e) Patients known or found to be allergic to pollens prevalent in the trial site locality during the period of the study (e.g. mountain cedar). f) Patients who have taken systemic or topical corticosteroids, long acting antihistamines or immunosuppressives within 4 weeks of selection (V1) or who take them within the course of the trial. Loratidine may not be taken within 10 days of entry. Short acting antihistamines may not be taken within 72 hours of entry except as comfort medication following nasal allergen challenge (oral antihistamines only). Patients excluded from the study for non-compliance with regard to prohibited medications but who have received one or more doses of the test medications will be included in the safety analysis.