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Anaphylaxis
Adrenaline first, adrenaline early, adrenaline in the thigh. Recognise it from airway, breathing or circulation problems after a trigger, give IM adrenaline without hesitating, repeat it if needed, and know when to start an infusion. Then send them home safely, with auto-injectors and an allergy referral. Built for revision, not live patient decisions.
Settle them, and check the basics
within minutesRed flags — what each should make you think
Anaphylaxis is ABC problems after a likely trigger. Skin changes are common but not always there. If in doubt, give IM adrenaline — it's very safe in the thigh. The danger is giving it late, not giving it when you didn't strictly need to.
The Resus Council UK algorithm
- 📞Call for help, remove trigger
- AdIM adrenaline 1:1000
- 5′Repeat after 5 minutes
- O₂High-flow oxygen
- IVFluid bolus
- ∞Refractory?
Understand the patient
recognise · grade · triggerWhen to call it anaphylaxis
- Sudden onset, rapid progression
- Airway (swelling, hoarseness, stridor) and/or Breathing (wheeze, tachypnoea, hypoxia) and/or Circulation (hypotension, collapse, tachycardia)
- Usually with skin or mucosal changes (urticaria, flushing, angioedema), but up to 1 in 5 have none
- Common triggers: food (nuts, shellfish), drugs (antibiotics, NSAIDs, anaesthetic agents, contrast), stings, latex
Adjuncts — no longer first-line
- Antihistamines (e.g. non-sedating oral cetirizine) — for skin symptoms only, after stabilisation
- Steroids — not routinely recommended in the emergency treatment (may be considered for refractory reactions or ongoing asthma/shock)
- Bronchospasm — treat as acute asthma once adrenaline given
- Beta-blocked patient not responding — consider glucagon, with senior advice
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Hoarse voice, stridor, drooling, swelling of tongue or uvula.
Clinical.
IM adrenaline, repeat; nebulised adrenaline can help as an adjunct; call anaesthetics/ENT early — intubation gets harder as swelling progresses.
Persistent respiratory or cardiovascular problems despite two appropriate doses of IM adrenaline.
Clinical.
Low-dose IV adrenaline infusion via a dedicated line with cardiac monitoring (critical care), keep giving IM adrenaline every 5 min until the infusion is running, rapid IV fluids. Cardiac arrest → ALS.
Symptoms return without re-exposure, usually within 12 hours. More likely after severe reactions or needing more than one dose.
Clinical.
Observe appropriately before discharge (see plan), and teach the patient to use the auto-injector and call 999.
Swelling of lips, tongue, face or gut with no urticaria or itch; on an ACE inhibitor, or family history (hereditary angioedema). Develops over hours.
Clinical; C4 and C1-esterase inhibitor levels for HAE.
Adrenaline may help less. Protect the airway. Specific treatment (icatibant, C1-esterase inhibitor concentrate) via senior/immunology. Stop the ACE inhibitor for good.
Paediatric IM adrenaline doses (1:1000)
- Under 6 months — 100–150 micrograms (0.1–0.15 mL)
- 6 months to 6 years — 150 micrograms (0.15 mL)
- 6–12 years — 300 micrograms (0.3 mL)
- Over 12 years — 500 micrograms (0.5 mL), or 300 micrograms if small or prepubertal
Investigate — what to order, when, and what it tells you
test with a question in mindMast cell tryptase
Monitoring
Document
How the plan comes together
disposition · handoverhome
Resolved. Observation: at least 2 h after resolution if good response to one dose and no risk factors; at least 6 h if 2 doses were needed or previous biphasic; at least 12 h if severe, needed more than 2 doses, severe asthma, or late presentation.
Give two adrenaline auto-injectors, train the patient, give written advice, avoid the trigger.
admit / ITU
Refractory reaction, airway involvement, ongoing hypotension or asthma, or social concerns.
Referral: everyone after anaphylaxis should be referred to a specialist allergy service.
If you're wondering whether to give adrenaline, give it. Then think about what comes next: tryptase timings, the observation period, two auto-injectors, and the allergy referral. Nicely done getting here.
Clerking template
copy or downloadAnaphylaxis — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 10 knownFrequently asked questions
quick answersWhat are the red flags for anaphylaxis?
- Stridor, hoarse voice, tongue swelling — think airway — anaphylaxis
- Wheeze, falling SpO₂ — think bronchospasm
- Hypotension, collapse — think anaphylactic shock
- No better after 2 doses of IM adrenaline — think refractory anaphylaxis
- On a beta-blocker — think may resist adrenaline
- Swelling without hives, on an ACE inhibitor — think bradykinin angioedema
What is the initial management of anaphylaxis?
- Call for help, remove trigger — stop the infusion or drug; lie flat with legs raised (sit up if breathing is the problem; left side if pregnant)
- IM adrenaline 1:1000 — adults and over-12s 500 micrograms (0.5 mL) into the anterolateral thigh
- Repeat after 5 minutes — if still unwell
- High-flow oxygen — titrate to saturations
- Fluid bolus — adults 500–1000 mL crystalloid if shocked, repeat
- Refractory? — after 2 doses of IM adrenaline: low-dose IV adrenaline infusion with critical care help
Always alongside senior support and your local guideline.
What diagnoses must you not miss in anaphylaxis?
- Airway obstruction — stridor · tongue swelling
- Refractory anaphylaxis — no better after 2 doses
- Biphasic reaction — recurrence hours later
- Bradykinin angioedema (mimic) — swelling, no hives, ACEi
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for anaphylaxis?
- Mast cell tryptase — Supports the diagnosis for the allergy clinic. Don't delay treatment for it.
- Monitoring — Continuous SpO₂, ECG and BP while unstable.
- Document — Likely culprit, timing, doses and times of adrenaline.
Admit or discharge: how is the plan decided for anaphylaxis?
- Home — Resolved. Observation: at least 2 h after resolution if good response to one dose and no risk factors; at least 6 h if 2 doses were needed or previous biphasic; at least 12 h if severe, needed more than 2 doses, severe asthma, or late presentation.
- Admit / itu — Refractory reaction, airway involvement, ongoing hypotension or asthma, or social concerns.
Is there a clerking template for anaphylaxis?
Yes — there is a free clerking template for anaphylaxis on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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