Anaphylaxis in Children

Definition and epidemiology

Anaphylaxis is a severe, life-threatening systemic hypersensitivity reaction that is usually rapid in onset. In children the commonest triggers are foods (cow’s milk, egg, peanut, tree nuts, seafood, wheat), followed by drugs (beta-lactams, NSAIDs) and insect venom. Lifetime prevalence is estimated at 0.3–0.5%, and food-triggered events dominate the paediatric age group. Fatalities are rare but disproportionately associated with delayed adrenaline administration, asthma comorbidity, and the upright/sitting posture during a hypotensive episode.

Clinical features

Anaphylaxis is a multi-system event. The mucocutaneous signs (urticaria, flushing, angioedema) are present in most but not all cases — their absence must never exclude the diagnosis.

• Skin/mucosa: urticaria, pruritus, flushing, lip/tongue/uvular swelling
• Respiratory: stridor, hoarseness, cough, wheeze, dyspnoea, hypoxia — the leading cause of death in children
• Cardiovascular: tachycardia, hypotension, collapse, syncope (relatively more common in adults)
• Gastrointestinal: crampy abdominal pain, vomiting, diarrhoea — an important early clue after a food trigger
• Neurological: sense of impending doom, drowsiness, confusion

Diagnosis

Anaphylaxis is highly likely when any one of the WAO/EAACI criteria is met: (1) acute onset with skin/mucosal involvement plus respiratory compromise or hypotension; (2) two or more organ systems involved rapidly after a likely allergen; or (3) hypotension after a known allergen for that patient. The 2020 WAO update added isolated laryngeal involvement or bronchospasm following a known/highly probable allergen.

See the full criteria: Anaphylactic Reaction Algorithm

Red flags

• Any airway compromise: stridor, hoarse voice, tongue swelling
• Persistent wheeze/hypoxia, especially in a known asthmatic
• Hypotension, pallor, floppiness, or reduced consciousness
• Rapidly progressive symptoms after a known food/drug/venom exposure
• Biphasic reaction risk — recurrence up to 72 h after apparent recovery

Management overview

Adrenaline is first-line and time-critical — give it early; there is no absolute contraindication.

1. IM adrenaline 0.01 mg/kg (1:1000), maximum 0.3 mg per dose in children (0.5 mg in adolescents/adults), into the anterolateral thigh. Repeat every 5 minutes if no improvement. Auto-injector equivalents: 0.15 mg (≈7.5–25 kg) and 0.3 mg (≥25 kg).
2. Position: lay the child flat with legs raised (or in a position of comfort if breathing is hard); never sit a hypotensive child up.
3. Airway, high-flow oxygen, and call for help/resuscitation team.
4. IV fluid bolus (crystalloid 10–20 mL/kg) for hypotension; repeat as needed.
5. Refractory cases: IV adrenaline infusion under monitoring, plus nebulised adrenaline/salbutamol for upper-airway/bronchospasm.
6. Adjuncts (second-line, never instead of adrenaline): antihistamines for itch/urticaria only; corticosteroids no longer routinely recommended for preventing biphasic reactions.
7. Observe 6–12 h (longer if severe, biphasic features, or asthma), then discharge with two adrenaline auto-injectors, a written emergency plan, allergen avoidance advice, and allergy/immunology referral.

In Indian settings, confirm auto-injector availability and counsel families on cost and import limitations; document the trigger and ensure school/caregiver action plans.

References

• WAO Anaphylaxis Guidance 2020
• EAACI Anaphylaxis Guideline (2021 update)
• Resuscitation Council UK — Emergency treatment of anaphylactic reactions (2021)
• IAP guidance on anaphylaxis

Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.