Ocular allergic disease may be the most common clinical problem involving the eye. Ocular allergy encompasses a spectrum of diseases characterized by type I hypersensitivity responses, and knowledge of the pathogenesis of these diseases is central to understanding the role of therapeutic agents used to treat these diseases. The differential diagnosis of ocular allergic disorders includes any disease in which the eye becomes red associated with itching, burning, and tearing. Many therapeutic options are available; however, treatment strategies may require a combination of prescriptive drops to control the disease.