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For some people, allergies just mean a runny nose and itchy eyes—symptoms that are inconvenient but not serious. For others, allergies mean eternal vigilance because contact with a trigger can result in anaphylaxis, a life-threatening allergic reaction.


Allergies (Seasonal and Perennial Allergic Rhinitis)

Allergies are an exaggerated immune reaction to normally harmless substances known as allergens. When a susceptible person is first exposed to an allergen, an immune response is activated. Later re-exposure may result in the release of substances, including histamine, triggering a range of reactions.
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