Anaphylaxis — Rapid | Doctor’s Passport

Synopsis

Recognise anaphylaxis clinically, give intramuscular adrenaline without delay, repeat and escalate treatment safely, distinguish common mimics and provide observation, auto-injector, allergy referral and risk-reduction follow-up.

Diagnose clinically: sudden illness with airway, breathing or circulation compromise, usually with skin or mucosal change; skin signs may be absent.
First-line and life-saving treatment is adrenaline 1 mg/mL intramuscularly into the anterolateral thigh; do not wait for IV access or antihistamine.
IM doses: older than 12 years 500 micrograms, 6 to 12 years 300 micrograms, 6 months to 6 years 150 micrograms, younger than 6 months 100 to 150 micrograms.
Repeat IM adrenaline after 5 minutes if ABC problems persist and call expert help early.
Lie flat with legs raised; if breathing is difficult allow supported sitting with legs extended. An unconscious child is placed in the recovery position and a pregnant adolescent on the left side.
Give high-flow oxygen, continuous monitoring and a rapid 10 mL/kg isotonic crystalloid bolus for shock, then reassess.
Two IM doses without adequate response defines refractory anaphylaxis: an experienced critical-care team starts a monitored IV adrenaline infusion; routine IV bolus adrenaline is unsafe.
Antihistamines relieve skin symptoms only after ABC stability; corticosteroids are not routine emergency treatment.
For children under 16, consider mast-cell tryptase when the cause may be venom, medicine-related or idiopathic, after resuscitation and ideally 1 to 2 hours from onset, no later than 4 hours, plus a later baseline.
Observation is risk-stratified from complete resolution: selected low-risk children may leave after 2 hours; higher-risk episodes need at least 6 or 12 hours under NICE NG258 criteria.
Before discharge provide two in-date adrenaline auto-injectors, demonstrate use, give a written emergency plan and refer to specialist allergy care.
Document the suspected trigger, time course, position, adrenaline times and response and notify school or nursery through the family plan.

Key red flags

Stridor, hoarseness, tongue or throat swelling, inability to vocalise, drooling or rapidly progressive facial swelling signals impending airway obstruction.

Severe wheeze, silent chest, cyanosis, exhaustion or falling consciousness indicates life-threatening respiratory failure.

Hypotension, collapse, confusion, pallor, clammy skin or persistent tachycardia indicates anaphylactic shock.

Persistent ABC compromise after two appropriate IM adrenaline doses is refractory anaphylaxis and needs expert IV adrenaline infusion and critical care.

Severe asthma, delayed adrenaline, a reaction to a small trigger dose, previous biphasic reaction or need for multiple adrenaline doses increases observation risk.

A child who improves while standing or walking can collapse from reduced venous return; sudden postural change must be avoided.

Investigation priorities

First-line serial ABC assessmentFirst stepFirst line

Diagnose clinically and track airway, oxygenation, perfusion and consciousness during treatment.

Management branches

Immediate treatmentIM adrenaline first

Sudden airway, breathing or circulation compromise suggests anaphylaxis.

Call for help, position safely and remove the trigger if feasible.
Give age-based adrenaline 1 mg/mL IM into the lateral thigh.
Give high-flow oxygen, monitor and obtain IV or IO access.
Repeat IM adrenaline after 5 minutes if ABC compromise persists.

Key medicines

Adrenaline 1 mg/mL intramuscularGive into the anterolateral thigh: older than 12 years 500 micrograms, although 300 micrograms may be appropriate if small or prepubertal; 6 to 12 years 300 micrograms; 6 months to 6 years 150 micrograms; younger than 6 months 100 to 150 micrograms. Repeat after 5 minutes if ABC compromise persists.Do not delay for IV access, antihistamine or diagnostic tests. Confirm the 1 mg/mL concentration; IV bolus administration outside cardiac arrest or exceptional specialist use can cause catastrophic error.

Isotonic crystalloidGive 10 mL/kg rapidly for anaphylactic shock and reassess perfusion, blood pressure and respiratory findings before further boluses.Adrenaline remains essential; use smaller reassessed aliquots and early vasoactive support if cardiac disease or fluid overload is a concern.

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