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(al″ĕr-jen′ik) Producing allergy. allergenicity (-jĕ-nis′ĭt-ē), n.


(ă-lĕr′jik) Pert. to, sensitive to, or caused by an allergen.

allergic reaction

A reaction resulting from hypersensitivity to an antigen. SEE: allergy for illus.; hypersensitivity.

allergic salute

A colloquial term for wiping the fingers or the hand upward across the nose, a sign of nasal inflammation resulting from allergies.


(al′ĕr-jist) A physician who specializes in diagnosing and treating allergies.


(al′ĕr-goyd″) [allergy + -oid] A chemically altered allergen used in immunotherapy to induce tolerance to an antigen. Allergoids differ from the allergens they derive from in that they produce an IgG antibody response stronger than an IgE (hypersensitivity) response.


(al′ĕr-jē) [allo- + Gr. -ergia, work, activity] An immune response to a foreign antigen that results in inflammation and organ dysfunction. Allergies range from annoying to life-threatening. They include systemic anaphylaxis, urticaria, eczematous dermatitis, hay fever, and rhinitis. They affect about 20% of Americans and can be triggered by inhalation (pollen, dust mites), direct contact (poison ivy), ingestion (drugs, foods), or injection (stinging insects, drugs). Allergic responses may be initiated and sustained by occupational exposure to allergens, and by foods, animals, fungal spores, metals, and rubber products. The most severe cases are often associated with Hymenoptera stings, penicillin products, radiological contrast media, and latex. SYN: hypersensitivity reaction. SEE: allergen; atopy.

ETIOLOGY: The immune system has two main functions: first, to identify germs and parasites that may harm the body; and second, to use toxic defenses against attacks by these organisms. Allergic reactions occur when immune functions are turned on by an agent richly endowed with alien antigens. Once the immune system has been sensitized, subsequent exposure results in the binding of specific immunoglobulins (esp. IgE) or the activation of immunologically active cells, e.g., mast cells, basophils, or T cells. These can release inflammatory chemicals (histamines, kinins, interleukins) that create allergic symptoms.

SYMPTOMS: Nasal inflammation, mucus production, watery eyes, itching, rashes, tissue swelling, bronchospasm, stridor, and shock are all symptoms of allergy.

DIAGNOSIS: A history of exposure and reaction is crucial to the diagnosis of allergy. Tests for specific allergies include skin prick tests, intradermal injections, or blood tests (measurements of antigen-specific immunoglobulins).

TREATMENT: Avoiding allergens is the first step in treatment. Effective drugs for allergic symptoms include antihistamines, corticosteroids, and epinephrine, depending on the severity of the reaction. Antigen desensitization (immunotherapy) may be used by experienced professionals, but this technique may occasionally trigger severe systemic reactions.

PATIENT CARE: Before any drug is given, ...

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