[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Anaphylaxis [Conditions](https://durgical.com/en/conditions/) · [Systemic conditions](https://durgical.com/en/conditions/) # Anaphylaxis Anaphylaxis is a severe, sudden allergic reaction that can block the airway, impair breathing or drop blood pressure within minutes; it can be fatal. Updated 2026-10-30 ## Structures involved Tap one to see what it is and open it in 3D. - [Epiglottis](https://durgical.com/en/anatomy/epiglottis/) - [Vocal folds](https://durgical.com/en/anatomy/vocal-fold/) - [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/) - [Tongue](https://durgical.com/en/anatomy/tongue/) - [Pharynx](https://durgical.com/en/anatomy/pharynx/) - [Trachea](https://durgical.com/en/anatomy/trachea/) - [Segmental bronchi](https://durgical.com/en/anatomy/segmental-bronchus/) - [Cricothyroid membrane](https://durgical.com/en/anatomy/median-cricothyroid-ligament/) - [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/) ## In biochemistry - [Catecholamines: synthesis and breakdown](https://durgical.com/en/biochemistry/topics/catecholamines-synthesis-and-breakdown/) - [Adrenaline](https://durgical.com/en/biochemistry/molecules/adrenaline/) - [Immunoglobulins (antibodies)](https://durgical.com/en/biochemistry/enzymes/immunoglobulins/) ## In immunology - [Mast cell and basophil](https://durgical.com/en/immunology/mast-cell-and-basophil/) - [Hypersensitivity: the four types compared](https://durgical.com/en/immunology/hypersensitivity-the-four-types-compared/) - [Type I hypersensitivity (immediate, IgE)](https://durgical.com/en/immunology/type-i-hypersensitivity/) - [Transfusion reactions](https://durgical.com/en/immunology/transfusion-reactions/) - [Latex and drug allergy](https://durgical.com/en/immunology/latex-and-drug-allergy/) - [Antibody structure and isotypes (IgG, IgA, IgM, IgE, IgD)](https://durgical.com/en/immunology/antibody-structure-and-isotypes/) - [IL-4, IL-5 and IL-13 (the Th2 cytokines)](https://durgical.com/en/immunology/il-4-il-5-and-il-13/) - [Fc receptors, BCR and TCR](https://durgical.com/en/immunology/fc-receptors-bcr-and-tcr/) - [Live vaccines: who should not receive them](https://durgical.com/en/immunology/live-vaccines-who-should-not-receive-them/) - [Events after vaccination (ESAVI) and how they are reported](https://durgical.com/en/immunology/events-after-vaccination-and-how-they-are-reported/) ## In the clinical exam - [Medicines, allergies and habits: tobacco, alcohol and other substances](https://durgical.com/en/clinical-exam/medicines-allergies-and-habits-tobacco-alcohol-and-other-substances/) ## In physiology - [Blood groups, transfusion and transfusion reactions](https://durgical.com/en/physiology/blood-groups-transfusion-and-transfusion-reactions/) - [Innate and adaptive immunity: overview](https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/) - [How edema forms](https://durgical.com/en/physiology/how-edema-forms/) - [Shock physiology](https://durgical.com/en/physiology/shock-physiology/) - [Local and humoral control of blood flow](https://durgical.com/en/physiology/local-and-humoral-control-of-blood-flow/) - [Adrenergic and cholinergic receptors](https://durgical.com/en/physiology/adrenergic-and-cholinergic-receptors/) ## Why it happens - [Histamine, serotonin, bradykinin and the plasma protein cascades](https://durgical.com/en/general-pathology/histamine-serotonin-bradykinin-and-the-plasma-protein-cascades/) - [Vascular changes in acute inflammation: vasodilation, leakage, exudate vs transudate](https://durgical.com/en/general-pathology/vascular-changes-in-acute-inflammation-vasodilation-leakage-exudate-vs-transudat/) - [Mediators of inflammation: the table to know](https://durgical.com/en/general-pathology/mediators-of-inflammation-the-table-to-know/) - [Shock: types, stages and the organs it damages](https://durgical.com/en/general-pathology/shock-types-stages-and-the-organs-it-damages/) - [Arachidonic acid metabolites in inflammation, and the drugs that block them](https://durgical.com/en/general-pathology/arachidonic-acid-metabolites-in-inflammation-and-the-drugs-that-block-them/) - [Edema and effusions: the four mechanisms](https://durgical.com/en/general-pathology/edema-and-effusions-the-four-mechanisms/) ## Show 1 more - [Eicosanoids: prostaglandins, thromboxanes and leukotrienes](https://durgical.com/en/biochemistry/topics/eicosanoids-prostaglandins-thromboxanes-and-leukotrienes/) ## What it is A severe, potentially life-threatening systemic hypersensitivity reaction that starts suddenly after exposure to a trigger and can compromise the airway, breathing or circulation within minutes. ## Who gets it Occurs at all ages: food is the main trigger in children, drugs and insect stings in adults. Many reactions happen outside hospital, so bystander recognition matters. In a parent survey of 969 schoolchildren aged 5–12 in Medellín, Colombia, 1.85% had had food-related anaphylaxis, and only 11% of these had an adrenaline autoinjector prescribed. ## Causes - Foods, such as peanuts, tree nuts, shellfish, fish, milk and egg - Drugs, especially antibiotics such as beta-lactams, non-steroidal anti-inflammatory drugs and some anaesthetic agents - Insect stings from bees, wasps and ants - Radiocontrast media and latex - Exercise-associated and idiopathic anaphylaxis, when no trigger is found ## Risk factors - Previous anaphylaxis or a known severe allergy - Asthma, particularly if poorly controlled, which increases the risk of a fatal reaction - Mastocytosis or other mast cell disorders - Cardiovascular disease and use of beta-blockers or ACE inhibitors, which can worsen or blunt the response to treatment - Cofactors such as exercise, alcohol, fever or concurrent infection - Delay in giving intramuscular adrenaline ## Pathophysiology In the classic form, the trigger cross-links IgE on mast cells and basophils, which release histamine, tryptase, leukotrienes and prostaglandins; some triggers act without IgE. These mediators cause vasodilation, capillary leak, smooth-muscle contraction and mucosal swelling, producing hypotension, bronchospasm, laryngeal oedema and hives. ## Classification - IgE-mediated (allergic) anaphylaxis - Non-IgE-mediated anaphylaxis (direct mast cell activation, e.g. some drugs and contrast media) - Uniphasic, biphasic (symptoms return hours later without new exposure) or protracted reactions - Severity grading systems exist, but definitions and scales vary between guidelines ## Symptoms and signs - Skin and mucosa: hives, flushing, itching, swelling of the lips, [tongue](https://durgical.com/en/anatomy/tongue/) or uvula (angioedema) - Airway: throat tightness, hoarseness, stridor, difficulty swallowing - Breathing: wheeze, cough, shortness of breath, low oxygen saturation - Circulation: dizziness, fainting, fast pulse, low blood pressure, collapse - Gut: cramping abdominal pain, vomiting, diarrhoea - A sense of impending doom; skin signs are absent in a minority of cases ## Red flags - Stridor, hoarse voice or swelling of the tongue or throat (airway threat) - Severe wheeze, cyanosis or falling oxygen saturation - Hypotension, collapse or loss of consciousness - No response to a first dose of intramuscular adrenaline - Return of symptoms hours after apparent recovery (biphasic reaction) ## Diagnosis **Clinical** A clinical diagnosis made at the bedside: rapid onset of [skin](https://durgical.com/en/anatomy/skin/) or mucosal signs with breathing or circulatory compromise, or typical involvement after exposure to a likely allergen. Widely used criteria (e.g. World Allergy Organization) guide recognition; treatment is not delayed for tests. **Tests** Serum tryptase drawn within a few hours of onset can support the diagnosis but a normal value does not exclude it. Later, an allergist may use skin tests or specific IgE to confirm the trigger. **Imaging** Not needed for diagnosis. ## Differential diagnosis - Vasovagal syncope - Acute asthma attack - Panic attack - Isolated angioedema (e.g. ACE-inhibitor or hereditary) - Septic or cardiogenic shock - Scombroid fish poisoning ## Goal of treatment Restore airway, breathing and circulation as fast as possible, stop mediator effects with adrenaline, watch for recurrence and prevent future episodes by identifying and avoiding the trigger. ## Treatment **Acute** Intramuscular adrenaline (epinephrine) into the outer thigh is the first-line treatment and is given without delay; it can be repeated if there is no improvement. **Acute** Remove the trigger if possible, call for help, position the patient lying flat with legs raised (or sitting if breathing is difficult), give high-flow oxygen and intravenous fluids. **Acute** Airway management by experienced staff when there is airway swelling, including intubation or a surgical airway in extreme cases. **Medical** Second-line drugs: inhaled beta-2 agonists for bronchospasm, H1 antihistamines for skin symptoms; glucocorticoids are often given but do not replace adrenaline. **Medical** Refractory anaphylaxis: adrenaline infusion and vasopressors in critical care; glucagon is considered in patients taking beta-blockers. **Follow-up** Observation after recovery because of the risk of a biphasic reaction; the length depends on severity and local guidelines. **Lifestyle** Discharge with an adrenaline auto-injector and training, a written emergency plan, referral to an allergist and venom immunotherapy when indicated. ## Drugs for this condition - [Epinephrine](https://durgical.com/en/pharmacology/epinephrine/) - [Hydrocortisone](https://durgical.com/en/pharmacology/hydrocortisone/) ## Complications - Airway obstruction and asphyxia - Refractory shock and cardiac arrest - Myocardial ischaemia, including Kounis syndrome (allergic acute coronary syndrome) - Hypoxic brain injury - Biphasic or protracted reactions ## Prognosis With early intramuscular adrenaline most patients recover fully. Deaths are uncommon and are linked to delayed adrenaline, airway compromise, asthma and cardiovascular disease. Recurrence is possible if the trigger is not identified. ## Prevention - Clear identification and documentation of the trigger in the medical record - Avoidance of the trigger and careful reading of food labels - Carrying an adrenaline auto-injector and knowing how to use it - Venom immunotherapy for selected people with insect-sting anaphylaxis ## Test yourself Think of the answer, then tap the question to see it. ## What is the first-line drug for anaphylaxis and by which route is it given? Adrenaline (epinephrine) given intramuscularly into the anterolateral thigh, without delay. ## What is a biphasic anaphylactic reaction? A return of symptoms hours after the first reaction resolved, without new exposure to the trigger; it is why patients are observed after recovery. ## Which blood test can support the diagnosis of anaphylaxis if drawn early? Serum mast cell tryptase, ideally within a few hours of onset; a normal value does not rule out anaphylaxis. ## Why do patients on beta-blockers pose a problem in anaphylaxis? They may respond poorly to adrenaline; glucagon is considered in refractory cases. ## What is the main mechanism of classic anaphylaxis? IgE-mediated degranulation of mast cells and basophils, releasing histamine and other mediators. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/anaphylaxis/) ## Related conditions - [Hypovolaemic shock](https://durgical.com/en/conditions/hypovolaemic-shock/) - [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Anaphylaxis](https://www.ncbi.nlm.nih.gov/books/NBK482124/) (StatPearls (NCBI Bookshelf), 2023); [Prevalence of Food-Hypersensitivity and Food-Dependent Anaphylaxis in Colombian Schoolchildren by Parent-Report](https://europepmc.org/article/PMC/PMC7915673) (Medicina (Kaunas, Lithuania), 2021) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/conditions/anaphylaxis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/anaphylaxis/