Type I hypersensitivity: IgE, mast cells and mediators
Sensitisation and elicitation in IgE-mediated allergy, what each mast cell mediator does, how to interpret tryptase, skin prick and specific IgE results, non-IgE mast cell activation, and how adrenaline, antihistamines, omalizumab and immunotherapy act.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Type I hypersensitivity is IgE-mediated immediate hypersensitivity. Reactions begin within minutes to 2 hours of exposure.
- It needs prior sensitisation. The first exposure makes IgE; a later exposure cross-links that IgE on mast cells and basophils.
- Preformed mediators (histamine, tryptase) act in minutes. Lipid mediators follow, and cytokines drive a late phase 4 to 8 hours later.
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Sources
- ASCIA Guidelines for Acute Management of AnaphylaxisAU/NZASCIA (Australasian Society of Clinical Immunology and Allergy), 2026 v2
- ASCIA allergy testing and mammalian meat allergy information for health professionalsAU/NZASCIA (Australasian Society of Clinical Immunology and Allergy)
- Definitions, criteria and global classification of mast cell disorders with special reference to mast cell activation syndromes: a consensus proposalInternational Archives of Allergy and Immunology (Valent et al), 2012
- Identification of a mast-cell-specific receptor crucial for pseudo-allergic drug reactions (MRGPRX2)Nature (McNeil et al), 2015
- Elevated basal serum tryptase identifies a multisystem disorder associated with increased TPSAB1 copy numberNature Genetics (Lyons et al), 2016
- Venom immunotherapy for preventing allergic reactions to insect stingsCochrane Database of Systematic Reviews (Boyle et al), CD008838, 2012
- Middleton's Allergy: Principles and Practice (9th ed.)Elsevier (Burks et al), 2020
- Last updated
- 14 November 2026
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