[Immediate and late phases of allergic rhinitis]

The allergic reaction of the human nasal mucosa (Type I Coombs and Gell) can be divided in an immediate- and a late-phase reaction. The degranulation of IgE-bearing mast cells is crucial for the initiation of the immediate phase (app. 30 min). Mediators of these cells - especially histamine - cause the typical allergic symptoms. Some of the patients develop a late-phase reaction after a symptom-free interval. Eosinophils migrate into the epithelial lining and release mediators. Furthermore, mast cells increase in number in the epithelium. Other cells like macrophages and T lymphocytes may be involved as well. While the released mediators cause an unspecific mucosal hyperreactivity, the increased number of IgE-bearing mast cells leads to a specific immunological augmentation of the nasal reaction ("priming effect"). The allergic pathomechanism can be reduced by drugs at different points.