Nasal congestion, detail of nasal mucosa, allergen, allergic reaction, treatments. Clinical phase of allergic rhinitis during contact with the allergen: the allergen is recognized by the IgE of the mast cells and immediately causes the release of histamine. A delayed reaction releases leukotrienes and cytokines which causes permanent inflammation. Below the inflammation stimulates the differentiation of lymphocytes into Th2 cells. These promote the proliferation of mast cells and the production of IgE specific for the antigen by the B lymphocytes. Specific immunotherapy reduces the production of IgE by the B lymphocytes and promotes the production of IgG which will neutralize the allergen. .