Understanding Allergy: Causes, Diagnosis, Treatment

Definition of allergy and exaggerated immune response

An allergy is an exaggerated immune response in which the body mistakenly treats an ordinarily harmless substance (an allergen) as a threat. This misidentification leads to allergic reactions and can result in allergic diseases such as hay fever (allergic rhinitis), allergic conjunctivitis, allergic asthma, atopic dermatitis, food allergies, and anaphylaxis. Allergic reactions occur when an allergen is recognized by the immune system, commonly involving IgE antibodies. IgE binds to the allergen and then to receptors on mast cells or basophils, triggering the release of inflammatory chemicals such as histamine. These mediators cause symptoms that may involve the skin (itchy rash, hives), airways (sneezing, coughing, wheezing, shortness of breath), and the gut (vomiting, diarrhea, abdominal discomfort).

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Common signs and symptoms across organ systems

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