This is a randomized, parallel, single center, double masked, vehicle controlled study. The purpose of this study is to determine the activity and safety of NS2 in patients with grass, tree or ragweed-pollen induced seasonal allergic conjunctivitis . Subjects will be randomized 1:1 to receive multiple doses of NS2 Ophthalmic Drops (0.5%) or NS2 Ophthalmic Drops Vehicle (0.0%).

Free aldehydes are thought to be related to inflammatory conditions such as allergic conjunctivitis. NS2, a small molecule aldehyde trap, is being evaluated to determine whether it may decrease inflammation by lowering aldehyde levels.

Inclusion Criteria:

• Graded conjunctival redness in at least one region (nasal or temporal) in each eye at any one time point (not necessarily the same time point) post-CAPT (Conjunctival Allergen Provocation Test) of >2
• Graded ocular itching at any one time point
• Visual acuity of at least 20/50 in each eye
• At least 2 year history of moderate to severe allergic conjunctivitis.
• Positive skin prick test to ragweed, grass and/or tree pollen within one year of Screening Visit (Visit 1).
• Ability to avoid any topical or systemic ocular medications during the entire study period.

Exclusion Criteria:

• Subjects must not have an ocular itching score >0 or a conjunctival redness score >1 prior to CAPT in either eye in any region (nasal or temporal) at Visits 2-4. I
• History of glaucoma, or Intraocular Pressure (IOP) over 25mmHg at the screening visit, or a history of elevated IOP within the past 1 year.
• Ocular surgery, including laser procedures, within the past 12 months of Visit 1.
• Use of glaucoma medications, antibiotics, antivirals, or topical cyclosporine within 1 month of the screening visit.
• History of dry eye syndrome, blepharitis, herpes simplex keratitis or herpes zoster keratitis.
• History of uveitis in the past 3 years.
• Presence of any ocular infection or active ocular inflammation (e.g. follicular conjunctivitis, allergic conjunctivitis) within 14 days prior to start of study (Visit 1).
• History of moderate to severe asthma or allergy induced asthma to the allergen that will be used in CAPT.
• Use of oral corticosteroids within 30 days of screening and throughout the study period; use of intranasal or inhaled corticosteroids within 14 days of screening and throughout the study period.
• Use of antihistamines (ocular, nasal, topical or oral) within 7 days prior to screening (Visit 1) and throughout the study period. Non-medicated artificial tears are allowed up to 72 hours before screening (Visit 1) and throughout the study period.

The period of time over which adverse events were collected for each subject was approximately 9 weeks.