What role does IgE play in Allergie?

IgE (immunoglobulin E) is the key antibody in type I (immediate) hypersensitivity reactions. Upon first exposure to an allergen (e.g., pollen, pet dander), B cells produce allergen‑specific IgE, which binds to mast cells and basophils. On re‑exposure, the allergen cross‑links these IgE molecules, triggering release of histamine, leukotrienes, and other mediators – clinically manifesting as sneezing, itching, hives, or anaphylaxis. Total IgE levels are often elevated in allergic individuals, but this is not diagnostic: parasitic infections, certain immunodeficiencies, or even normal variation can raise IgE. Specific IgE tests (e.g., ImmunoCAP) are widely used, but a positive result alone does not confirm clinical allergy – correlation with symptoms and, if needed, provocation testing is required. The evidence for IgE’s central role is human‑strong (fulfilling Koch’s postulates for allergy), but test interpretation must be done by a physician. Caveat: high total IgE without symptoms is not proof of allergy; low IgE does not rule out allergy.