Anaphylaxis is a systemic allergic reaction thought to be caused via Initial production of allergen-specific lgE antibodies and subsequent triggering of mast cells. However, as confirmed in this thesis, mast cell activation does not occur in ~30% patients and does not account for the rapid amplification of the Immune response. This thesis Investigates the Involvement of other cell types using a variety of approaches. For the first time, neutrophil activation was demonstrated during acute human anaphylaxis. This novel finding represents a potential mechanism driving the rapid amplification phase of anaphylaxis, opening up new avenues for Improved diagnosis and treatment.