Anaphylaxis

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups: see disclaimer

INITIAL

all patients: acute onset

1st line – cardiopulmonary assessment + supportive measures

Plus – intramuscular epinephrine (adrenaline)

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Plus –

intramuscular epinephrine (adrenaline)

Treatment recommended for ALL patients in selected patient group

Immediate administration of adequate doses of intramuscular epinephrine will decrease patient mortality and morbidity.[12][76] All patients with signs of a systemic reaction, especially hypotension, airway swelling, or difficulty breathing, should receive immediate intramuscular epinephrine in the anterolateral thigh.[76][82][83][84][85]

This dose may be repeated every 5 to 15 minutes as needed.[6][12][76][86] The anterolateral thigh is superior over intramuscular administration in the deltoid or subcutaneous injection.[87][88]

It is usual practice to provide a prescription for two epinephrine auto-injectors after any episode of anaphylaxis due to the risk of severe anaphylaxis or a biphasic recurrence requiring multiple doses, although it may be reasonable to adopt a risk-stratified approach.[55][90] The patient or caregiver should carry both at all times and be familiar with their use.[83] For children at risk of anaphylaxis, the epinephrine auto-injectors should be prescribed in conjunction with a personalized written emergency plan.[83][91] American Academy of Pediatrics: allergy and anaphylaxis emergency plan Opens in new window

Primary options

epinephrine (adrenaline): children: 0.01 mg/kg (as a 1:1000 solution) intramuscularly every 5-15 minutes, maximum 0.3 mg/dose; adults: 0.3 to 0.5 mg (as a 1:1000 solution) intramuscularly every 5-15 minutes

Plus – assess and secure airway

Plus – oxygen

Plus – intravenous fluids

cardiopulmonary arrest

Plus – CPR + intravenous epinephrine (adrenaline)

severe refractory hypotension

Plus – intravenous epinephrine (adrenaline)

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Plus –

intravenous epinephrine (adrenaline)

Treatment recommended for ALL patients in selected patient group

Intravenous epinephrine is administered to patients in cardiopulmonary arrest, and to profoundly hypotensive patients who have not responded to intravenous fluids and several doses of intramuscular epinephrine.[12][96]

Continuous intravenous infusion of epinephrine, titrated to effect, is reserved for experienced practitioners. No intravenous dose regimen is universally recognized.

Primary options

epinephrine (adrenaline): children: 0.01 mg/kg (as a 1:10,000 solution) intravenously every 5 minutes, maximum 0.3 mg/dose; adults: 0.1 mg (as a 1:10,000 solution) intravenously every 5 minutes

Consider – intravenous glucagon

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Consider –

intravenous glucagon

Treatment recommended for SOME patients in selected patient group

In patients prescribed beta-blockers for coronary artery disease (CAD), both the medication and the underlying comorbidity complicate the treatment of severe anaphylaxis. The beta-blocker counteracts epinephrine (adrenaline) by limiting heart rate and compromising cardiac output. CAD limits cardiac reserve, which might compound the hypotension occurring due to the release of vasoactive mediators. The stresses of hypotension, tachycardia, and endogenous or iatrogenic adrenergic agents may cause myocardial ischemia by reducing perfusion during diastole. Glucagon may be used to overcome beta blockade, but the resulting tachycardia can be detrimental in patients with severe CAD.[6][55] Therefore, early consultation of a cardiologist may be considered.

Primary options

glucagon: children: 0.02 to 0.03 mg/kg (maximum 1 mg/dose) intravenously initially, followed by 5-15 micrograms/minute infusion, titrate according to response; adults: 1-5 mg intravenously initially, followed by 5-15 micrograms/minute infusion, titrate according to response

persistent respiratory symptoms

Plus – inhaled beta-2 agonist

symptomatic hives and rhinorrhea

Consider – H1 antagonist + H2 antagonist

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Consider –

H1 antagonist + H2 antagonist

Treatment recommended for SOME patients in selected patient group

Use of H1 and H2 antagonists is limited to relief of itching, hives, and rhinorrhea. Their use should never delay or replace the use of intramuscular epinephrine (adrenaline).[92][93] Most antihistamines can be given intravenously, intramuscularly, or orally. In perioperative anaphylaxis, no evidence for harm in the administration of antihistamines was reported in a large UK audit.[27] Oral administration may be sufficient for very mild allergic reactions but not anaphylaxis.

Primary options

diphenhydramine: children: 1-2 mg/kg intravenously/intramuscularly; adults: 25-50 mg intravenously/intramuscularly

and

cimetidine: children: consult specialist for guidance on dose; adults: 300 mg intravenously as a single dose

post-emergency stabilization

Consider – corticosteroids

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Consider –

corticosteroids

Treatment recommended for SOME patients in selected patient group

Corticosteroids may be prescribed as adjunctive therapy after the administration of epinephrine (adrenaline).[1][12] Corticosteroids may decrease the risk of symptoms associated with anaphylaxis, including urticaria. Guidelines published in 2020 advise against administering corticosteroids to prevent biphasic anaphylaxis. This is based on limited evidence suggesting that there is no clear benefit in terms of risk reduction.[12]

Although corticosteroids are not routinely recommended for the acute management of anaphylaxis, they may be considered after the administration of epinephrine for refractory reactions or where an acute asthma exacerbation may have contributed to the severity of anaphylaxis.[94]

Primary options

methylprednisolone: children and adults: 1-2 mg/kg/day intravenously

prednisone: children and adults: 0.5 to 1 mg/kg/day orally

ONGOING

patients with identified allergen

1st line – immunotherapy

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1st line –

immunotherapy

Venom immunotherapy may be recommended for prevention of systemic reactions in patients with a history of anaphylaxis subsequent to insect sting.[12][74] [ ] The treatment is highly effective at preventing these systemic reactions.[95] Venom immunotherapy increases the risk of adverse systemic reactions during treatment.[95]

Avoidance of food allergens remains the preventive mainstay of food-induced anaphylaxis.[12][96] Subcutaneous, epicutaneous (via absorbed patch), oral, and sublingual immunotherapy routes have been assessed. Studies suggest that while treatment may lead to desensitization, few patients attain tolerance.[96] Food-allergy-specific immunotherapy continues to be researched; it has historically been associated with adverse reactions, including anaphylaxis.[96] Currently, oral immunotherapy peanut allergy is approved for use under specialist supervision by the Food and Drug Administration (FDA) for the mitigation of allergic reactions including anaphylaxis, which may occur with exposure to peanuts.[97] See Food allergy for further information.

Drug desensitization may be considered to induce temporary drug tolerance in patients with immunoglobulin E-mediated drug-induced anaphylaxis who require the causal drug, and where there is no effective alternative option.[12][74] Drug desensitization should be performed by experienced clinicians in an appropriate setting.

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Anaphylaxis

Treatment algorithm

all patients: acute onset

cardiopulmonary assessment + supportive measures

intramuscular epinephrine (adrenaline)

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

assess and secure airway

oxygen

intravenous fluids

cardiopulmonary arrest

CPR + intravenous epinephrine (adrenaline)

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

severe refractory hypotension

intravenous epinephrine (adrenaline)

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

intravenous glucagon

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

persistent respiratory symptoms

inhaled beta-2 agonist

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

symptomatic hives and rhinorrhea

H1 antagonist + H2 antagonist

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

post-emergency stabilization

corticosteroids

Primary options

These drug options and doses relate to a patient with no comorbidities.

Primary options

Drug choice, dose and interactions may be affected by the patient's comorbidities. Check your local drug formulary.

Primary options

patients with identified allergen

immunotherapy