Anaphylaxis in paediatrics

Key points

• Anaphylaxis is a serious systemic hypersensitivity reaction that is usually rapid in onset and may cause death. Severe anaphylaxis involves life-threatening compromise of airway, breathing and/or circulation and can occur without typical skin features or circulatory shock.
• Initial treatment is to remove the allergen if possible and give intramuscular (IM) adrenaline. In a child with possible anaphylaxis and known asthma, always give adrenaline first, then asthma medicines.
• Lay the child flat or sitting with legs extended, and do not allow standing or walking for at least 1 hour after symptoms have resolved.
• Antihistamines, corticosteroids and leukotriene antagonists should not be given, and adrenaline should not be given subcutaneously.
• Every child should be observed for at least 4 hours after the last adrenaline dose. Before discharge, children and families should receive education, an individualised action plan and follow-up, and, unless the cause was a medicine, two adrenaline devices with training.

Overview

Anaphylaxis in children is a clinical diagnosis, so emergency treatment is guided by the clinician's judgement rather than a precise definition. IM adrenaline is the first treatment, given with the child in the right position, and the child is then observed for at least 4 hours. Respiratory symptoms predominate in children and may resolve before treatment or arrival at hospital, but they should still be recognised.

Recognising anaphylaxis

Airway signs are difficult or noisy breathing, tongue (not lip) swelling, throat swelling or tightness, a hoarse voice or change in cry, and drooling in infants. Breathing problems are the most common in children: difficulty talking, wheeze and a persistent, usually sudden-onset, cough. Circulatory signs include a pale and floppy infant, persistent dizziness, sudden drowsiness, collapse, low blood pressure, a fast or slow heart rate and cardiac arrest. Severe or persistent gastrointestinal symptoms (abdominal pain, vomiting) point to anaphylaxis of any cause, but mild symptoms count only when caused by insect stings or injected medicines and not when caused by food. Skin signs alone do not indicate anaphylaxis, and they are absent in 10 to 20% of cases. No investigations are needed in most children, and serum tryptase has no role in acute management.

Treatment

Treatment is IM adrenaline, with the dose chosen by age and weight from the guideline's chart. Adrenaline devices are matched to weight: EpiPen Jr (150 µg) for 7.5 to 20 kg, EpiPen (300 µg) for over 20 kg and Anapen (500 µg) for over 50 kg. Refractory anaphylaxis is anaphylaxis that still needs treatment for persisting respiratory or cardiovascular symptoms after 2 appropriate IM doses. It needs expert critical care advice and an adrenaline infusion, and IV bolus adrenaline is not recommended except in peri-arrest situations. The guideline gives a peripheral infusion recipe for non-tertiary hospitals, started at 5 mL/kg/hr and titrated to response with continuous monitoring.

Observation, admission and discharge

All children are observed in a setting equipped to manage deterioration for at least 4 hours after the last adrenaline dose, or after symptom onset if no adrenaline was given. Overnight admission is recommended after more than 2 adrenaline doses, an adrenaline infusion, IV fluid resuscitation or circulatory involvement, and with a history of biphasic reaction or a more severe initial reaction, poorly controlled asthma, an isolated home location, late-evening presentation or anaphylaxis to monoclonal antibody therapy. A child can be discharged when clinically stable and not needing adrenaline for at least 4 hours. The discharge checklist includes updating the medical record with the suspected allergen, an individualised ASCIA Action Plan, two adrenaline devices with training and correct positioning, optimised asthma management and prompt referral to a paediatrician or allergy specialist. Children with medicine (drug) anaphylaxis are generally not prescribed an adrenaline device.

Timing and fatal anaphylaxis

Reactions usually develop within minutes: 5 to 15 minutes for injected allergens such as insect stings, typically by 30 minutes for swallowed food, and usually 1 to 6 hours for oral medicines. Fatal anaphylaxis is rare in Australia, at about 1 per million population, and in children it is mainly triggered by food. Cardiorespiratory arrest more than 4 hours after the first exposure is rare. Risk factors are delayed adrenaline or emergency response, upright posture, poorly controlled asthma, peanut, tree nut or seafood allergy, adolescence and heart or lung conditions, and the severity of a previous reaction does not predict future risk.

Frequently asked questions

What is the first treatment for anaphylaxis in a child?

Remove the allergen if possible and give IM adrenaline. If the child has known asthma, give adrenaline first and asthma medicines afterwards.

Should antihistamines or steroids be given?

No. Antihistamines, corticosteroids and leukotriene antagonists should not be given in anaphylaxis, and adrenaline should be given IM rather than subcutaneously.

How long should a child be observed?

At least 4 hours after the last adrenaline dose, or after symptom onset if none was given, with overnight admission in the situations listed by the guideline.

Source

The Royal Children's Hospital Melbourne. Anaphylaxis. Clinical Practice Guidelines, endorsed by the Paediatric Improvement Collaborative. Last updated October 2025. This page is a summary prepared by Medpresso from the original publication. It is not a substitute for the full text or for medical advice.