Anaphylaxis
A severe, rapidly developing allergic reaction that is a medical emergency. Triggered by foods, insect stings, medicines or other allergens, it can cause breathing difficulty, throat swelling, a widespread rash and a drop in blood pressure. It is treated immediately with adrenaline (epinephrine).
What it is
Anaphylaxis is a severe, whole-body allergic reaction that comes on quickly — usually within minutes to a couple of hours of exposure to a trigger — and can be life-threatening. It happens when the immune system reacts massively to an allergen, with mast cells releasing a flood of histamine and other chemicals that affect the whole body. Common triggers are foods (such as peanuts, tree nuts, shellfish, milk and egg), insect stings, medications (such as some antibiotics), and, less often, latex or exercise; sometimes no trigger is found. The reaction typically involves two or more body systems: the skin (widespread hives, flushing, swelling of the face, lips or tongue), the airway and breathing (throat tightness, a hoarse voice, wheeze, difficulty breathing), the circulation (a drop in blood pressure causing dizziness, collapse or fainting), and the gut (cramps, vomiting). A feeling of impending doom is common. Anaphylaxis is a clinical emergency recognised on these features — it is not diagnosed by waiting for a blood test. The immediate, life-saving treatment is intramuscular adrenaline (epinephrine), given without delay, followed by emergency care. Afterwards, a tryptase level and allergy testing help confirm it and identify the trigger.
Key lab markers
- The diagnosis is clinical and immediate — it is recognised on symptoms and treated at once; no test should delay adrenaline.
- Tryptase — a correctly timed blood sample during or soon after the reaction, compared with a later baseline, can confirm mast-cell activation after the event.
- Total IgE and specific IgE (or skin-prick) allergy testing — done later to identify the trigger.
- Baseline tryptase — a persistently high level afterwards may point to an underlying mast-cell disorder.
Symptoms
- Comes on rapidly, usually within minutes of exposure
- Difficulty breathing, wheeze, or a tight or swollen throat
- Swelling of the face, lips, tongue or throat
- Widespread hives (urticaria), flushing or itching
- Dizziness, feeling faint, or collapse (from a drop in blood pressure)
- Vomiting, abdominal cramps
- A sense of impending doom or severe anxiety
- Often a known allergy or an obvious trigger (food, sting, medicine)
Related symptoms
When to discuss with a doctor
Anaphylaxis is a medical emergency — if someone has sudden difficulty breathing, throat or facial swelling, a widespread rash, or feels faint or collapses after contact with a likely allergen, call emergency services immediately and use an adrenaline auto-injector (such as an EpiPen) straight away if one is available, injected into the outer thigh; then lie the person down and seek emergency care even if they improve, because symptoms can return. Never wait to 'see if it settles', and never rely on antihistamines alone for a severe reaction. Anyone who has had anaphylaxis needs an allergy assessment to identify the trigger, a management plan, and usually an adrenaline auto-injector to carry. Mediora.AI can show a tryptase result and allergy tests that help confirm the reaction and identify the cause afterwards, but anaphylaxis itself is treated instantly on clinical grounds — recognising it and giving adrenaline fast is what saves lives.