Airway swelling, stridor, wheeze, or shock after exposure: give IM adrenaline 500 micrograms immediately and call for help. Position by symptom: lie flat with legs raised if hypotensive, sit up if breathing difficulty, left lateral if pregnant.
Triggers
- Food (nuts, shellfish), drugs (antibiotics, NSAIDs)
- Venom, latex, contrast
- Idiopathic: still treat as anaphylaxis
IM adrenaline by age (1:1000)
- Adult and child over 12: 500 micrograms (0.5 mL)
- Child 6 to 12: 300 micrograms; 6 months to 6 years: 150 micrograms
- Repeat after 5 min if no improvement
- Anterolateral thigh
Mild allergic reaction
- Urticaria or itch, no airway or CVS
- Antihistamine, observe
- Not anaphylaxis
Anaphylaxis
- Airway, breathing or circulation involved
- IM adrenaline 500 micrograms
- Repeat at 5 min, give fluids
Refractory / arrest
- No response after 2 IM doses
- IV adrenaline infusion (senior)
- ALS if in arrest
Anaphylaxis treatment
1
1. Adrenaline
IM adrenaline into the anterolateral thigh. Remove the trigger (stop any infusion). High-flow oxygen. Call for senior and resuscitation help.
IM adrenaline into the anterolateral thigh. Remove the trigger (stop any infusion). High-flow oxygen. Call for senior and resuscitation help.
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2
2. Fluids
Rapid IV crystalloid bolus (500 to 1000 mL adult, 10 mL/kg child) if hypotensive. Reassess.
Rapid IV crystalloid bolus (500 to 1000 mL adult, 10 mL/kg child) if hypotensive. Reassess.
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3
3. Refractory (after 2 doses)
Start an IV adrenaline infusion with senior or critical care. Consider glucagon if on beta-blockers. Chlorphenamine and steroids are no longer routine first-line.
Start an IV adrenaline infusion with senior or critical care. Consider glucagon if on beta-blockers. Chlorphenamine and steroids are no longer routine first-line.
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4
4. Observe and discharge
Observe (commonly 6 to 12 h, longer if severe or on beta-blockers). Serial mast cell tryptase. Two adrenaline auto-injectors, training, and allergy clinic referral.
Observe (commonly 6 to 12 h, longer if severe or on beta-blockers). Serial mast cell tryptase. Two adrenaline auto-injectors, training, and allergy clinic referral.
Biphasic risk
- Can recur up to 72 h later
- Longer observation if severe, needed repeat adrenaline, or on beta-blockers
- Safety-net advice on discharge
Pitfalls
- Giving IV adrenaline as a bolus on the ward (infusion only)
- Delaying adrenaline to give antihistamine or steroid
- Standing or sitting a hypotensive patient up
- Not taking tryptase samples
MedPrep - www.medprep.uk - Educational revision aid only. Not clinical guidance. Doses are adult examples; check the BNF, current guidelines and local policy, and seek senior advice. Nov 2026