Anaphylaxis

A severe, life-threatening allergic reaction that comes on quickly and needs emergency treatment with adrenaline.

AllergyEmergencyLast updated: 21 October 2026

Quick Summary

Primary Symptoms

Swelling of the throat or tongue, difficulty breathing, wheezing, dizziness, fainting, hives and vomiting, within minutes of exposure.

Common Treatments

Adrenaline (epinephrine) injection immediately, call 112, then hospital care.

Risk Factors

Allergies to foods (such as peanuts and shellfish), insect stings, medicines (such as antibiotics) and latex.

OverviewSymptomsCausesTreatmentFAQ

Overview

Anaphylaxis affects the whole body. The airways can swell and blood pressure can drop dangerously.

People at risk should carry an adrenaline auto-injector and know how to use it.

Symptoms

Breathing difficulty

Wheezing or noisy breathing.

Swelling

Of lips, tongue, throat or face.

Dizziness and collapse

From low blood pressure.

Hives

Widespread itchy rash.

Causes & Risk Factors

Biological Causes

A sudden release of chemicals from immune cells in response to an allergen.

Key Risk Factors

  • Food allergies Peanuts, tree nuts, shellfish and milk.
  • Insect stings Bees and wasps.
  • Medicines Antibiotics and painkillers.

Management & Treatment

01. Adrenaline

Inject into the outer thigh straight away.

02. Call 112

Even if symptoms improve.

03. Prevention

Avoid triggers, carry two auto-injectors and an allergy plan.

Frequently Asked Questions

Should I lie down?
Lie flat with legs raised; sit up if breathing is difficult.
Can antihistamines treat anaphylaxis?
No, adrenaline is the essential treatment.

Sources and further reading

Last updated 21 October 2026. For more detail, see these trusted health organisations.