Seasonal allergic conjunctivitis is the most common form of allergic ocular disease. Changes in the conjunctiva include a visible increase in the type and number of cells provoking allergy symptoms, usually in spring  and in fall. The aforementioned cell types, such as mast cells and eosinophils, interact and release a variety of allergic mediators when exposed to seasonal aeroallergens such as tree or grass pollen. Preformed  mediators are released in an immediate phase, and newly  formed mediators appear approxomately eight to twenty-four hours after exposure. These mediators have overlapping biological functions that contribute to the typical ocular itching, redness, and watery discharge associated with allergic eye disease.