Anaphylaxis is a serious generalized or systemic hypersensitivity reaction that is rapid in onset and potentially fatal.

Diagnosis can be made if it is acute in onset of minute to several hour duration that involves the skin, mucosal tissue or both plus having signs & symptoms either respiratory or cardiovascular compromise.

It involves immunological response with IgE, IgG or immune complexes. Non-immunological mechanisms are also involved and termed as nonallergic anaphylaxis that is relatively uncommon in children.

Protracted, severe anaphylaxis are reactions occurring up to 32 hours despite aggressive management.



  • A serious generalized or systemic hypersensitivity reaction that is rapid in onset and potentially fatal
  • Involves immunological response with IgE, high-affinity IgE receptors, mast cells, basophils, release of cytokines, chemokines, and chemical mediators of inflammation such as histamine and tryptase
  • IgG-mediated anaphylaxis has been reported in humans after administration of dextran or monoclonal antibodies
  • Nonimmunological mechanisms are also involved and termed as nonallergic anaphylaxis
    • Relatively uncommon in children


  • Food allergy - most common cause in the community setting
    • Eg peanuts, tree nuts, fish, shellfish, milk, eggs
  • Medications (eg penicillins, beta-lactams, cephalosporins, NSAIDs, muscle relaxants, anticancer chemotherapy drugs, biological modifiers and monoclonal antibodies [eg Omalizumab]) and latex - common in the hospital setting
  • Insect sting
  • Food-induced anaphylaxis associated with exercise - affects teenagers
    • Anaphylaxis occurs when exercise takes place within 2-4 hours of ingestion of a specific food
    • May be food-independent or food-dependent; may be encountered after ingestion of celery, shellfish, wheat
  • Idiopathic anaphylaxis
    • When the trigger of the anaphylaxis is unknown or cannot be identified despite a thorough history, allergen skin tests, IgE levels and provocation tests
  • Allergen immunotherapy

Signs and Symptoms

  • The longer the symptoms develop the less severe the overall reaction
  • Grading the severity of clinical symptoms as 1 to 5 based on the organ system most affected may be helpful in the diagnosis and timely administration of Epinephrine


  • Most frequent manifestations occuring in more than 90%
  • May be delayed or absent in up to 20% of cases
  • Include urticaria, angioedema (including periorbital edema, conjunctival swelling), flushing, pruritus (may begin on palms and soles)


  • Occur in up to 70% of episodes
  • Include rhinorrhea, nasal congestion, throat tightness, dysphagia, hoarseness, ‘barky’ cough, stridor, wheeze, dyspnea


  • Symptoms occur in up to 45% of episodes
  • Include oral pruritus, nausea, vomiting, diarrhea, crampy abdominal pain


  • Occur in up to 10-30% of episodes
  • Include dizziness, tachycardia, chest pain, hypotension and collapse


  • Include lightheadedness, “sense of doom”, confusion, loss of consciousness, headache, seizure
Digital Edition
Asia's trusted medical magazine for healthcare professionals. Get your MIMS JPOG - Malaysia digital copy today!
Editor's Recommendations
Most Read Articles
Dr Joslyn Ngu, 22 Feb 2018

Beta blockers have been dropped out of major guidelines as first-line therapy for hypertension but there may be exceptions to this rule, says a cardiologist.