IgE and non-IgE mechanisms in ocular allergy.

Various forms of conjunctival disease have traditionally been referred to by the umbrella term "allergic conjunctivitis," on the assumption that they are all caused by a Gell and Coombs type I hypersensitivity reaction. Recent evidence disputes this classification, however, and suggests that other mechanisms may also be responsible for the complex clinical features of conjunctival disease. Among these are non-IgE-mediated activation of mast cells, late-phase reactions, and nonspecific conjunctival hyperreactivity. The authors suggest that the pathophysiology of allergic eye disease is multifactorial, which explains the different clinical pictures seen in different patients. Both IgE-mediated and non-IgE-mediated mechanisms may cause an immediate reaction as well as allergic inflammation, and nonspecific hyperreactivity may occur both as a result of allergic inflammation and as an independent mechanism in nonallergic conjunctival disease.