Anaphylaxis

Anaphylaxis is an acute systemic (multi-system) and severe Type I Hypersensitivity allergic reaction in humans and other mammals. The term comes from the Greek words ana (against) and phylaxis (protection). Anaphylaxis occurs when a person or animal is exposed to a trigger substance, called an allergen, to which they have already become sensitized. Minute amounts of allergens may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, skin contact, injection of an allergen or, in rare cases, inhalation.

Anaphylactic shock, the most severe type of anaphylaxis, occurs when an allergic response triggers a quick release from mast cells of large quantities of immunological mediators (histamines, prostaglandins, leukotrienes) leading to systemic vasodilation (associated with a sudden drop in blood pressure) and edema of bronchial mucosa (resulting in bronchoconstriction and difficulty breathing). Anaphylactic shock can lead to death in a matter of minutes if left untreated.

An estimated 1.24% to 16.8% of the population of the United States may suffer from anaphylactic reactions, 1% of whom may die as a result. Most common presentation is sudden cardiovascular collapse (88% of reported cases of severe anaphylaxis).citation needed]

Researchers typically distinguish between "true anaphylaxis" and "pseudo-anaphylaxis." The symptoms, treatment, and risk of death are identical, but "true" anaphylaxis is always caused directly by degranulation of mast cells or basophils that is mediated by immunoglobulin E (IgE), and pseudo-anaphylaxis occurs due to all other causes. The distinction is only important for researchers who are studying mechanisms of allergic reactions. Due to the word "pseudo", it may frustrate patients who feel they are being told that a life-threatening allergic reaction isn't "real".