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.


Immediate Management

Prompt assessment and treatment are critical as death can ensue rapidly

  • Rapid assessment of airway, breathing, circulation and level of consciousness
    • Remove triggering allergens if possible (eg induce vomiting if food-induced, stop drug intake/infusion, etc)
  • Place the patient in the supine position with the lower extremities elevated if tolerated (left lateral position for vomiting patients or in a comfortable position for patients with dyspnea)
  • Administer Epinephrine 1:1000 dilution (1 mg/mL) at a dose of 0.01 mL/kg (Max dose: 0.3-0.5 mL or 0.3-0.5 mg) every 5-15 minutes, until condition stabilizes
    • Dose is equivalent to 10 mcg/kg
    • Intramuscular (IM) injection into the lateral side of the thigh is the best route and site to give epinephrine to treat an anaphylactic reaction
    • Injection in the thigh produces more rapid absorption and higher plasma epinephrine concentration than IM injection in the arm
  • Inhaled Epinephrine via metered dose inhalers or nebulizers may be beneficial to treat laryngeal edema or persistent bronchospasm in cases where intravenous (IV) route cannot be obtained or despite a previous IM Epinephrine dose
  • Repeated doses of Epinephrine are administered until clinical improvement is achieved
    • If no improvement after 3-4 doses, patient should be transported to an emergency medical facility


Epinephrine Intravenous (IV) Infusion

  • Indicated during cardiac arrest or in profoundly hypotensive patients who have failed to respond to several inj doses of Epinephrine and IV fluid replacement
  • May be prepared by adding 1 mg (1 mL) of 1:1000 dilution of Epinephrine to 250 mL of D5W to yield 4 mcg/mL
    • Infused at a rate of 1-4 mcg/minute; max of 10 mcg/minute for adolescents
  • An alternative is the “rule of 6”: 0.6 x body weight (kg) = number of mg diluted in 100 mL of saline, then 1 mL/hour delivers 0.1 mcg/kg/minutes
  • Continuous cardiac monitoring is recommended due to potential for lethal arrhythmias

Antihistamines (H1- and H2-receptor antagonists)

  • Used in the treatment of urticaria-angioedema or pruritus related to allergic reaction
    • There is no evidence of their efficacy in anaphylaxis treatment
  • Combination of H1- and H2-receptor antagonists has been reported to be more effective in anaphylaxis than H1-receptor antagonist alone

Inhaled Bronchodilators

  • Eg Salbutamol
  • Additional treatment for persistent bronchospasm not responsive to Epinephrine
  • Given intermittently or continuously, depending on the patient’s symptoms and the availability of cardiac monitoring


  • Used to prevent recurrence of symptoms of protracted anaphylaxis
  • May be given in patients with a history of idiopathic anaphylaxis and asthma, and in patients who experience severe or prolonged anaphylaxis
    • Recommended IV/PO dose of Methylprednisolone or equivalent formulation is 1-2 mg/kg up to 125 mg per dose
    • Should be discontinued once full recovery is achieved
  • For mild-moderate attacks, oral administration of Prednisone is recommended
  • For severe anaphylaxis, Methylprednisolone IV is recommended to modulate the late-phase response


  • Eg Dopamine
  • Given if Epinephrine and fluid resuscitation have failed to alleviate hypotension

Indications for self-injectable Epinephrine

Absolute indications for prescribing self-injectable Epinephrine

  • History of cardiovascular or respiratory reaction to an allergen (eg food, latex, insect sting)
  • Food-induced anaphylaxis associated with exercise
    • At least 2 auto-injections should be prescribed and carried at all times by patients at risk for food-induced anaphylaxis
  • Patients with food allergy and co-existent persistent asthma
  • Idiopathic anaphylaxis

Relative indications for prescribing self-injectable Epinephrine

  • Previous reaction to small amounts of food
  • History of only a previous mild reaction to a tree nut or peanut
  • Severe food allergic reaction in an adolescent
  • Remote location without rapid access to medical facility
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