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  • Anaphylaxis: A severe, systemic hypersensitivity reaction characterized by multi-system involvement, which can lead to shock, airway compromise, and even death if not treated promptly.


  • Common triggers include foods (e.g., nuts, shellfish), medications (e.g., antibiotics, non-steroidal anti-inflammatory drugs), insect stings (e.g., wasps, bees), and latex.
  • Some cases are idiopathic, with no identifiable cause.


  • Anaphylaxis involves an IgE-mediated immune response, leading to the release of histamine and other mediators from mast cells and basophils. This causes vasodilation, increased vascular permeability, and smooth muscle contraction.

Clinical Features

  • Skin: Urticaria (hives), angioedema, flushing, or pruritus.
  • Respiratory: Dyspnoea, wheezing, cough, and throat tightness, potentially leading to airway obstruction.
  • Cardiovascular: Hypotension, tachycardia, and in severe cases, shock.
  • Gastrointestinal: Abdominal pain, vomiting, and diarrhoea.
  • Neurological: Dizziness or loss of consciousness.


  • Primarily clinical, based on the rapid onset of symptoms affecting the skin/mucosa AND at least one of the following: respiratory compromise, reduced blood pressure or associated symptoms, persistent gastrointestinal symptoms.
  • Serum tryptase levels may be elevated post-event and can support the diagnosis.

Management (UK Guidelines)

  1. Immediate Actions:
    • Remove the Trigger: If possible, immediately remove the source of the allergen (e.g., stop drug administration).
    • Call for Help: Activate emergency medical services or alert the emergency response team in a hospital setting.
  2. Medication:
    • Adrenaline: The first-line treatment for anaphylaxis.
      • Administer an intramuscular injection into the mid-outer thigh.
      • Adult and child >12 years: 500 micrograms IM (0.5 mL)
      • Child 6ā€“12 years: 300 micrograms IM (0.3 mL)
      • Child 6 months to 6 years: 150 micrograms IM (0.15 mL)
      • Child <6 months: 100ā€“150 micrograms IM (0.1ā€“0.15 mL)
      • Repeat every 5 minutes as necessary.
      • Antihistamines and Corticosteroids: Although not primary treatments, they can be used adjunctively to help control symptoms. Antihistamines can help with itching and hives, while corticosteroids can prevent delayed reactions.
  3. Airway Management:
    • Give high flow oxygen
    • Ensure the airway is open and clear. In severe cases, intubation may be required.
  4. Fluid Resuscitation:
    • Administer intravenous fluids to counteract hypotension, especially in the case of shock.
      • Adults: 500ā€“1000 mL
      • Children: 10 mL/kg
  5. Observation and Monitoring:
    • Monitor vital signs and clinical state continuously. Patients should be observed for at least 6-12 hours as biphasic reactions can occur.
  6. Long-Term Management:
    • Allergen Identification and Avoidance: Refer to an allergy specialist for identification of specific allergens and advice on avoidance strategies.
    • Adrenaline Auto-Injector: Prescribe for patients at risk of future anaphylaxis and ensure they and their families are trained in its use.
    • Patient Education: Provide information on anaphylaxis recognition and the importance of wearing medical alert identification.

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