An immediate (and potentially health- or life-threatening) allergic reaction produced by the patient producing immunoglobulin E (IgE) antibodies to a foreign substance (antigen) to which he or she is allergic; the affected tissues release histamine which causes local or systemic attack. An example is the pain, swelling, rash, fever and sometimes collapse that may occur after a wasp sting or ingestion of peanut in a particularly sensitive person. On rare occasions a person may be so sensitive that anaphylaxis may lead to profound SHOCK and collapse which, unless the affected person receives urgent medical attention, including injection of ADRENALINE, intravenous fluids and oxygen may cause death. (See also ALLERGY; IMMUNITY.)