[The cellular players in allergy].

Ocular allergy, with a significant increase of prevalence, is one of the most usual disease of the ocular surface. But, in a same entity, it means different kinds of clinical diseases with acute hayfever conjunctivitis, usually easy to diagnose, but also chronic perennial forms without any functional or clinical specificity among others ocular surface diseases. These clinical aspects are underlain by complex cellular mecanisms which are essentially located inside the conjunctiva. Initially, allergen cross the lacrimal tear film, the first natural barrier of the eye, then in the conjunctival epithelium, meet the antigen presenting cells, the Langerhans cells, lymphocytes and all the others components of the inflammatory and allergic reaction, including mast cells and eosinophils. The cornea could also be involved in allergic diseases, mostly in severe ones such as vernal or atopic keratoconjunctivitis, but most often, its pathology is due to direct cytotoxic effect of chemical mediators, such as eosinophil proteins, rarely results from mechanical or immunological pathways.