local anaphylaxis

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Related to local anaphylaxis: generalized anaphylaxis

lo·cal an·a·phy·lax·is

the immediate, transient kind of response that follows the injection of antigen (allergen) into the skin of a sensitized individual and is limited to the area surrounding the site of inoculation.
See also: skin test.
Farlex Partner Medical Dictionary © Farlex 2012

lo·cal an·aph·y·lax·is

(lō'kăl an'ă-fi-lak'sis)
The immediate, transient kind of response that follows the injection of antigen (allergen) into the skin of a sensitized individual and is limited to the area surrounding the site of inoculation.
See also: skin test
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


(an?a-fi-lak'sis) [ ana- + (pro)phylaxis]
A sudden, severe allergic reaction between an allergenic antigen and immunoglobulin E (IgE) bound to mast cells, which stimulates the sudden release of immunological mediators locally or throughout the body. The first symptoms occur within minutes, and a recurrence may follow hours later (late-stage response). Anaphylaxis can only occur in someone previously sensitized to an allergen because the initial exposure causes immunoglobulin E (IgE) to bind to mast cells. Anaphylaxis may be local or systemic. Local anaphylactic reactions include hay fever, hives, and allergic gastroenteritis. Systemic anaphylaxis produces peripheral vasodilation, bronchospasm, and laryngeal edema and can be life-threatening. anaphylactic (-lak'tik), adjective


IgE antibodies react when the allergen is introduced a second time. The mast cells release packets containing chemical mediators (degranulators) that attract neutrophils and eosinophils and stimulate urticaria, vasodilation, increased vascular permeability, and smooth muscle spasm, esp. in the bronchi and gastrointestinal tract. Chemical anaphylactic mediators include histamine, proteases, chemotactic factors, leukotrienes, prostaglandin D, and cytokines, e.g., TNF-a and interleukins 1, 3, 4, 5, and 6. The most common agents triggering anaphylaxis are food, drugs, and insect stings. Local anaphylactic reactions are also commonly triggered by pollens, e.g., hay fever, allergic rhinitis, allergic asthma. See: anaphylactic shock


Local anaphylaxis causes such signs as urticaria (hives), edema, warmth, and erythema to appear at the site of allergen-antibody interaction. In systemic anaphylaxis the respiratory tract, cardiovascular system, skin, and gastrointestinal system are involved. The primary signs are urticaria, angioedema, flushing, wheezing, dyspnea, increased mucus production, nausea and vomiting, and feelings of generalized anxiety. Systemic anaphylaxis may be mild or severe enough to cause shock when massive vasodilation is present.


Local anaphylaxis is treated with antihistamines or, occasionally, epinephrine if the reaction is severe. Treatment for systemic anaphylaxis includes protection of the airway and administration of oxygen; antihistamines, e.g., diphenhydramine or cimetidine to block histamine H1 and H2 receptors; IV fluids to support blood pressure; and vasopressors, e.g., epinephrine or dopamine, to prevent or treat shock. Epinephrine is also used to treat bronchospasm. Generally, drugs are given intravenously; drugs may also be given intramuscularly, e.g., diphenhydramine, or endotracheally, e.g., epinephrine. In mild cases they may be given subcutaneously. Corticosteroids may be used to prevent recurrence of bronchospasm and increased vascular permeability.

Patient care

Prevention: A history of allergic reactions, particularly to drugs, blood, or contrast media, is obtained. The susceptible patient is observed for reaction during and immediately after administration of any of these agents. The patient is taught to identify and avoid common allergens and to recognize an allergic reaction.

Patients also should be taught to always wear tags identifying allergies to medications in order to prevent inappropriate treatment during an emergency. Those who have had an anaphylactic reaction and are unable to avoid future exposure to allergens should carry a kit containing a syringe of epinephrine and be taught how to administer it. Patients allergic to the venom of Hymenoptera (bees, wasps, hornets) can receive desensitization.

active anaphylaxis

Anaphylaxis resulting from injection of an antigen.

aggregate anaphylaxis

Anaphylaxis stimulated by antigen-antibody complexes in the blood, which in turn cleave complement and degranulate mast cells and basophils.

biphasic anaphylaxis

Protracted anaphylaxis.

exercise-induced anaphylaxis

Anaphylactoid reaction.

idiopathic anaphylaxis

Anaphylaxis of uncertain cause. Some evidence suggests it may occasionally result from exposure to food allergens.

local anaphylaxis

Arthus reaction.

passive anaphylaxis

Anaphylaxis induced by injection of serum from a sensitized animal into a normal one. After a few hours the latter becomes sensitized.

passive cutaneous anaphylaxis

Abbreviation: PCA
A laboratory test of antibody levels in which serum from a sensitized person is injected into the skin. Intravenous injection of an antigen accompanied by Evan's blue dye at a later time reacts with the antibodies produced in response to the antigen, creating a wheal and blue spot at the site, indicating local anaphylaxis.

protracted anaphylaxis

A recurrence of anaphylactic symptoms (bronchospasm, hypotension) several hours after successful treatment for anaphylaxis, in the absence of a new exposure to a triggering antigen.
Synonym: biphasic anaphylaxis

systemic anaphylaxis

A reaction between IgE antibodies bound to mast cells and an allergen that causes the sudden release of immunological mediators in the skin, respiratory, cardiovascular, and gastrointestinal systems. The consequences may range from mild, e.g., itching, hives, to life-threatening (airway obstruction and shock).
Medical Dictionary, © 2009 Farlex and Partners
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