Mechanism (IgE-mediated mast cell/basophil degranulation → histamine and mediators → skin/mucosal, respiratory, cardiovascular, and GI end-organ effects — adrenaline is the only first-line life-saving drug (EAACI 2021, WAO 2020, AAP 2023))
Max 0.5 mg/dose · Duration: PRN · 0.01 mg/kg (10 mcg/kg) IM — repeat q5–15 min PRN; anterolateral thigh; max 0.5 mg/dose
• Diagnostic criteria (EAACI/WAO): acute onset illness with skin/mucosal involvement (urticaria, flush, angioedema) AND respiratory compromise and/or hypotension/end-organ dysfunction; OR ≥2 of skin/mucosa, respiratory, hypotension, GI symptoms after likely allergen exposure.
• IM injection site: **anterolateral mid-outer thigh** — may be given through clothing; do NOT give IM into buttock (reduced absorption); subcutaneous route is inferior — use IM (RCUK, ASCIA, AAP).
• Repeat IM adrenaline q5–15 min if no clinical improvement — no absolute maximum number of doses in life-threatening anaphylaxis; prepare for second dose while monitoring response (EAACI, WAO, RCUK).
• Auto-injector weight bands (prescription/discharge): **7.5–<20 kg** → 0.15 mg (EpiPen Jr / Auvi-Q 0.15); **≥20 kg** → 0.3 mg (EpiPen / Auvi-Q 0.3); **<7.5 kg** or when calculated dose <0.1 mg → draw 0.01 mg/kg from ampoule with syringe (more precise than fixed device); Auvi-Q 0.1 mg for 7.5–25 kg where available (ASCIA 2024, AAP 2023).
• Volume from 1:1000 solution = dose in mg (e.g. 0.2 mg = 0.2 mL); use 1 mL syringe for small volumes; do NOT use IV strength (1:10 000) for IM injection (EAACI, RCUK).
Max 5 mg/dose · Duration: PRN · Bronchospasm/wheeze — 2.5 mg (<5 yr) or 5 mg (≥5 yr) nebulized, repeat q20 min; or 0.15 mg/kg (min 2.5 mg, max 5 mg); adjunct to adrenaline, not substitute (EAACI, WAO, AAP)
Enter weight on Kids to calculate doses
Cetirizine • p.o. • 0.25–0.25 mg/kg/dose • 1×/day
Max 10 mg/dose · Duration: Once · H1 antihistamine — non-sedating preferred; give AFTER adrenaline; relieves urticaria/itch only, no effect on airway or hypotension (ASCIA, EAACI); fixed ages: 6–12 mo 2.5 mg, 1–6 yr 5 mg, >6 yr 10 mg
Max 8 mg/dose · Duration: Once · NOT routine first-line — ASCIA/EAACI do NOT recommend routine steroids for acute anaphylaxis; if used per local protocol for prolonged symptoms: 0.15 mg/kg IV/PO once (max 8 mg); does NOT prevent biphasic reactions reliably; never delay adrenaline (ASCIA 2024, EAACI, WAO)
Max 5 mg/dose · Duration: PRN · 2.5 mg (<5 yr or <20 kg) or 5 mg (≥5 yr) nebulized q20 min PRN; weight-based 0.15 mg/kg (min 2.5 mg, max 5 mg) — adjunct for wheeze/bronchospasm (EAACI, WAO, AAP)
• Salbutamol: wheeze, bronchospasm, or respiratory distress persisting after adrenaline — nebulized 2.5–5 mg q20 min PRN; continue oxygen if hypoxic (EAACI, WAO, AAP).
• Cetirizine (or loratadine): preferred oral H1 after patient is stable — treats urticaria/pruritus only; safe in infants ≥6 months (cetirizine); do NOT delay adrenaline (ASCIA 2024, EAACI).
• Diphenhydramine IV: avoid routine IV in young children — sedation, anticholinergic effects, and potential hypotension; use oral non-sedating H1 when possible; IV only if no oral route and patient stable enough (AAP, ASCIA).
• H2 blocker (famotidine): optional adjunct to H1 for cutaneous symptoms — NOT recommended routinely by EAACI/ASCIA; weak evidence for added benefit (EAACI 2021).
• Dexamethasone: NOT routine — do not use as reason to delay adrenaline or observation; if local protocol uses steroids for prolonged reactions, prednisolone 1 mg/kg (max 50 mg) PO is alternative to dexamethasone 0.15 mg/kg (RCUK allows hydrocortisone/prednisolone consideration; ASCIA advises against routine steroids).
Enter weight on Kids to calculate doses
Clinical notes
• Diagnostic criteria (EAACI/WAO): acute onset with skin/mucosal involvement AND (respiratory compromise OR hypotension/end-organ dysfunction); OR ≥2 of skin/mucosa, respiratory, hypotension, persistent GI symptoms after likely allergen exposure — treat as anaphylaxis and give IM adrenaline without delay.
• ABCDE priorities: **A**irway (position, prepare for intubation if stridor/edema) · **B**reathing (oxygen if SpO₂ <94%, salbutamol for wheeze) · **C**irculation (IM adrenaline first, then IV fluids 10–20 mL/kg crystalloid bolus if hypotension persists) · **D**isability (AVPU, glucose) · **E**xposure/trigger removal and monitoring.
• Patient positioning: supine with legs elevated (improves venous return); if vomiting or unconscious place in recovery position (lateral); **avoid sudden standing or sitting** — risk of fatal ''empty ventricle''/postural hypotension after adrenaline (RCUK, ASCIA, WAO).
• Oxygen: give high-flow oxygen if SpO₂ <94%, respiratory distress, or cyanosis — target SpO₂ 94–98%; nebulized salbutamol via oxygen-driven nebulizer if wheeze (RCUK, EAACI).
• IV fluids: crystalloid bolus 10–20 mL/kg (max 1 L) if hypotension persists after IM adrenaline — treat anaphylactic shock; reassess after each bolus; second-line vasopressors/IV adrenaline infusion only in refractory shock under specialist care (RCUK, WAO).
• EAACI Guidelines — Anaphylaxis (pediatric and adult) (2021)
• WAO — Anaphylaxis guidance update (2020)
• AAP Clinical Report — Anaphylaxis (2023)
+ 2 more
• Resuscitation Council UK — Emergency treatment of anaphylaxis (2021)
• ASCIA — Acute management of anaphylaxis (pediatric dosing and auto-injectors) (2024)
