The purpose of this study is to evaluate the safety and effect of nasal carbon dioxide in the treatment of Seasonal Allergic Rhinitis

This multi-center, randomized, double-blind, placebo-controlled, parallel group trial will evaluate the efficacy and safety of a nasal, non-inhaled administration of carbon dioxide (CO2) in patients with seasonal allergic rhinitis. An estimated 500 patients who meet the eligibility criteria will be enrolled into this study at approximately 25 sites to ensure that approximately 400 patients are randomized and complete the study.

Inclusion Criteria:

• Able to read and understand informed consent and voluntarily consent to sign the informed consent form
• Able to comply with the requirements of the protocol (e.g., complete the diary within the protocol-specified window)
• Minimal 2-year history of Fall seasonal allergic rhinitis requiring pharmacotherapy
• Positive skin test to one or more Fall seasonal allergen (e.g., ragweed, birch pollen, etc.)
• Females of childbearing potential must commit to using an acceptable method of birth control and have a negative pregnancy test

Exclusion Criteria:

• History of asthma (other than mild intermittent)
• Acute or significant sinusitis or upper respiratory infection within 14 days of enrollment
• Existing serious medical condition (e.g., severe emphysema) that precludes participation
• Females who are pregnant or breast-feeding and/or who plan to become pregnant or to breast-feed during the study participation or within 7 days after the last study drug administration
• Initiation of immunotherapy or have a change in immunotherapy dose within the 6 months preceding enrollment (if on immunotherapy, the same dose must be maintained throughout the trial)
• Planned travel outside the study area for the duration of study period
• Participation in another clinical study within 30 days of planned enrollment date and for the duration of the study
• Participation in a previous study with Nasal CO2