- The basic pathogenic sequence of Type I Hypersensitivity reactions is discussed on its own page. Anaphylaxis is essentially a severe Type I Hypersensitivity reaction in which there is a catastrophic, system-wide degranulation of mast cells and basophils. Degranulation of these cells causes release of potent vasoactive, bronchoactive, and inflammatory mediators throughout the body. The ultimate cause of systemic hypoperfusion and thus shock in anaphylaxis is likely release of enormous amounts of histamine which cause wide-spread inappropriate arteriolar vasodilation and thus a severe drop in systemic vascular resistance.
- Skin: urticaria, pruritis, erythema
- Lung: Bronchoconstriction and mucus hypersecretion
- GI System: Cramping abdominal pain, diarrhea, and vomiting
- Larynx: Laryngeal edema can cause hoarseness, stridor, and in severe cases total airway obstruction