Conjunctivitis is one of the most common ocularaffections in clinical practice and when of allergic etiologypresents difficulties and peculiarities both in differentialdiagnosis and therapeutical approaches. Clinically, itspresentation can range from mild seasonal symptoms toperennial forms coursing with intense and very uncomfortableocular itching and tearing, or to visual loss due tocorneal involvement. In the recent years, new insights intothe cellular and molecular mechanisms of allergic diseasehave come into view, along with the development of newdrugs acting in several pathways of the allergic reaction. Theaim of «Ocular Allergy» is to summarize, in a monograph, thecurrent knowledge of the immunopathology, diagnosis andtherapeutical approaches of these affections.