Hypersensitivity: Anaphylactic (Type I)

Type I hypersensitivity reactions occur in individuals who have been previously sensitized to a specific allergen. They are the result of allergen recognition by immunoglobulin E on mast cells and basophils and cause a variety of symptoms such as itching or tingling of the lips, tongue or throat; nausea, vomiting and diarrhoea; sneezing, runny nose and wheezing, shortness of breath and coughing. In some cases, the reaction can be so severe that the circulatory system shuts down and tracheal swelling occurs, leading to a lifethreatening condition known as anaphylaxis.