Anaphylaxis is a multisystem hypersensitivity reaction that is characterised by acute onset with characteristic skin features, with the potential for cardio-respiratory complications. 

Signs and Symptoms

  • Respiratory/chest – cough, wheeze, stridor, tongue swelling
  • Cardiovascular – palpitations, tachycardia, bradycardia, hypotension
  • Neurological – headaches, dizziness, altered consciousness
  • Gastrointestinal – nausea, vomiting, diarrhoea, abdominal pain
  • Dermatological – urticarial rash, erythema/flushing, angio-oedema


Anaphylaxis is a diagnosis made on a clinical basis. 


Below are a number of differentials based on different presentations of anaphylaxis:

  • Tissue swelling – urticaria
  • Upper airway oedema – acute oesophageal reflux (sudden onset of painful throat “swelling”)
  • Flushing syndromes
    • Peptide-secreting tumours (eg, carcinoid syndrome, VIPomas)
    • Alcohol-related
    • Medullary carcinoma of thyroid
    • Red man syndrome (associated with vancomycin infusion)
  • Neurological syndromes – Epileptic seizure and stroke
  • Other causes of collapse – Vasovagal episodes and shock (other causes)
  • Acute respiratory distress – Asthma, panic disorders and laryngospasm


  • Remove allergen that precipitated the reaction
  • Place the child in the supine position and keep them still 
  • Inject intramuscular adrenaline (10 micrograms/kg or 0.01 ml/kg of 1:1000), into the lateral thigh. Repeat after 5 minutes if there is no improvement.

See the DFTB module on Anaphylaxis: