General Medical Information

The Allergic Reaction

Richard L. Mabry

The immunologic mechanism of the allergic response is discussed in detail in Chapter 8. The primary reaction involved in nasal allergy is a Gell and Coombs type I immediate (anaphylactic) hypersensitivity reaction. Allergen-specific immunoglobulin E (IgE), which is produced after allergen exposure, is bound to mast cells or basophils. This IgE reacts with its unique allergen to cause mast cell degranulation and release of histamine and other mediators of inflammation, such as prostaglandins and leukotrienes. The reaction begins within 2 to 5 minutes of such an antigen-antibody reaction and reaches a peak after about 15 minutes. A second (late) phase is the result of mediator release from cells (neutrophils, eosinophils) and occurs about 4 to 6 hours after the acute phase. These reactions take place under the influence of numerous mediators called cytokines. Understanding this prototypical allergic reaction and its effect on the upper respiratory tract allows the practitioner to consider therapeutic measures in light of site and mode of action for either preventing or alleviating the results of the allergic event.