Eligibility Criteria:
Inclusion Criteria
* Able to comprehend and grant a witnessed, written informed consent prior to any study procedures.
* Female participants of child bearing age must have a negative urine pregnancy test at Screening Visit and subsequent visits. In addition, female participants must be using a medically acceptable form of birth control.
* History of seasonal allergic rhinitis for at least 2 years with symptoms during the ragweed pollen season requiring pharmacotherapy.
* A positive skin test by prick method to ragweed pollen at the Screening Visit. A positive skin prick test will be defined as a ragweed pollen-induced wheal greater than 3 mm larger in diameter than diluent control (measurements will be made 15-20 minutes after application).
* Must be capable of faithfully completing the diary and of attending regularly scheduled study visits.
* Must intend to remain in the ragweed pollen area during the entire ragweed season.
* Willing to avoid prohibited medications for the periods indicated in the protocol.
* Participants must meet pretrial eligibility requirements for trial enrollment (acceptable medical history, physical examination results, normal electrocardiogram and acceptable laboratory test results).
* Participants must have a baseline serum Immunoglobulin E (IgE) level greater than 10 and less than 700 IU/mL.
Exclusion Criteria
* weigh less than 30 kg or more than 120 kg.
* pregnant or lactating.
* history of severe anaphylactoid (non-IgE mediated) or anaphylactic reactions).
* history of immunotherapy within the past 10 years, if received one full year of immunotherapy, or within the past 5 years if received less than one year of immunotherapy.
* known hypersensitivity to trial rescue medication (fexofenadine HCl).
* taking beta-adrenergic antagonists in any form.
* taking allergic ophthalmologic medication.
* clinically significant perennial rhinitis that would interfere in assessment of ragweed-induced seasonal allergic rhinitis symptoms.
* Presence of a severely deviated nasal septum, septal perforation, structural nasal defect or large nasal polyps causing obstruction.
* History of an upper respiratory or sinus infection requiring treatment with an antibiotic within 2 weeks prior to Screening Visit.
* Documented evidence of acute or significant chronic sinusitis, as determined by the Investigator.
* Asthma (either history of, abnormal spirometry, \[forced expiratory volume in 1 second (FEV1) less than 80% predicted\] or use of asthma medications).
* Chronic or intermittent use of inhaled, oral, intra-muscular, or intra-venous corticosteroids; or chronic or intermittent use of topical corticosteroids within 4 weeks of Visit Screening Visit.
* Chronic use of medications (e.g., tricyclic antidepressants) that would affect assessment of the effectiveness of the study medication.
* Rhinitis medicamentosa.
* History or presence of significant renal, hepatic, neurologic, cardiovascular, hematologic, metabolic, cerebrovascular, respiratory, gastrointestinal or other significant medical condition including, autoimmune or collagen vascular disorders, aside from organ-specific autoimmune disease limited to the thyroid that in the Investigator's opinion could interfere with the study or require medical treatment that would interfere with the study.
* History of cancer other than basal cell carcinoma of the skin.
* History within the past year of excessive alcohol intake or drug addiction.
* Current smokers, greater than 10 pack year history, or participants who quit smoking less than one year prior to Screening.
* Use of any prohibited concomitant medications during the washout period (i.e., before screening) and throughout the study period.
* Participants currently undergoing immunotherapy.
* Participants with clinically significant abnormality on 12-lead Electrocardiogram (ECG) on screening visit.
* Treatment with an experimental, non-approved drug, or investigational drug within the past 30 days.
* Participants with a history of noncompliance to medical regimens and participants who are considered potentially unreliable.
* Previous treatment with a monoclonal antibody for any reason including anti-IgE in any form (e.g., omalizumab).
* Participants with known hypersensitivity to trial drug ingredients (i.e., sucrose, histidine, polysorbate 20) or related drugs (i.e., monoclonal antibody; polyclonal gamma-globulin).