Ocular Allergy has become one of the common clinical ailments in many patients who encounter with perennial allergens like animal dander, dust and molds. Understanding of immunologic mechanisms, differential diagnosis and clinical features help physicians to treat better these allergic patients. Target tissue of the eye is the conjunctiva, mucous membrane, inside of the upper and lower eyelids. This chapter explains the mechanism of allergens and their contact with eye and thus eliciting immune response to get rid of it is explained in detail in the chapter. Signs and symptoms of allergy include the triad of conjunctival redness, itching and swelling; some patients with blepharitis, dry eye and irritative nonallergic conjunctivitis also complain of itching. Different types of ocular allergy include Seasonal and perennial allergic conjunctivitis caused mainly by airborne allergens, vernal keratoconjunctivitis which occurs in warm climatic conditions, Atopic keratoconjunctivitis or atopic eczema, and Giant papillary conjunctivitis caused by inert substances. Treatments for allergy are mainly customized to each patient depending on the severity of the symptoms; and are mainly given oral antiallergics on a regular basis. Avoidance, cold compress, oral antihistamines, mast-cell stabilizers are some of the generally given treatment options for patients with ocular allergy. Corticosteroid eye drops are given to patients with severe symptoms.