Allergic diseases are widely prevalent with one study showing about 35% of families interviewed in the United States experiencing some form of allergy and more than 50% of those affected reporting eye symptoms. Worldwide, allergies are estimated to affect 20% of the population. Allergic pathogenesis is therefore the focus of intensive research and many studies have focused on the role of histamine in ocular allergy and other atopic disorders. Histamine is a biogenic amine that plays a key role in allergic inflammation. This molecule is closely associated with immunoglobulin E (IgE)-mediated...