Anaphylaxis is rare but fast. A child can go from itchy lips after a bite of cashew to struggling to breathe within minutes. The parents who manage it best are the ones who have rehearsed the steps — who know exactly where both auto-injectors are, who know which thigh to inject and how to hold it, and who understand that adrenaline goes in first, before antihistamines, before waiting to see if things settle on their own.
The hesitation to use an auto-injector when you are not 100% sure is understandable, but the maths is heavily weighted toward acting early. Adrenaline given in error to a child who turns out not to be having anaphylaxis is very unlikely to cause harm — at worst, brief shakiness and a fast heart rate. Adrenaline given too late to a child who is having anaphylaxis can be the difference between life and death.
Healthbooq (healthbooq.com) covers allergy and emergency health in children.
What Anaphylaxis Is
Anaphylaxis is a severe systemic allergic reaction affecting multiple organ systems at once. It is caused by mass release of histamine and related mediators from mast cells after exposure to a trigger in someone who has been previously sensitised. The result is vasodilation (dropping blood pressure), increased vascular permeability (swelling), smooth muscle contraction (bronchospasm and gut cramps), and excess mucus production.
The Resuscitation Council UK defines anaphylaxis as likely when a patient develops sudden illness, usually within minutes of allergen exposure, involving life-threatening airway, breathing, or circulation problems, usually with skin or mucosal changes. Most cases involve two or more body systems simultaneously.
Triggers in Children
In UK children, the most common triggers are foods. Peanuts and tree nuts (cashew, walnut, pistachio, Brazil nut) lead by some distance. Milk and egg are major triggers in younger children, and many of these resolve through childhood. Fish, shellfish, sesame, and wheat account for a smaller proportion. Insect stings (bee and wasp) are the second main category. Drug allergy — penicillin and NSAIDs like ibuprofen — accounts for a smaller share.
Important to know: the severity of a reaction to a particular allergen can vary unpredictably between exposures. A child who has previously had only mild reactions to a food is not protected from a severe future reaction. This is exactly why all children with confirmed food allergy who have had any systemic symptoms are prescribed adrenaline auto-injectors.
Recognising Anaphylaxis
Hives and angioedema on their own are extremely common allergic reactions and do not constitute anaphylaxis. The critical question is whether life-threatening features are developing, and the rule of thumb is two or more body systems involved.
Airway: throat tightening, stridor (high-pitched noise on breathing in), hoarse voice, difficulty swallowing, drooling. The child may point to their throat or say "my tongue feels funny."
Breathing: wheeze, shortness of breath, fast breathing. In young children, look for intercostal recession (skin pulling in between the ribs), nasal flaring, or grunting.
Circulation: pallor, cold clammy skin, racing pulse, faintness, loss of consciousness. Hypotension may follow. Young children may go floppy or unusually quiet — both are warning signs.
Skin: hives, swelling of face and lips, generalised flushing. Present in around 80-90% of cases — but absence of skin features does not exclude anaphylaxis.
Gut: nausea, vomiting, abdominal cramping. Persistent vomiting after a known trigger is a treat-as-anaphylaxis sign.
A key principle: anaphylaxis can present without prominent skin features, particularly with sting-triggered and exercise-triggered reactions. Sudden circulatory collapse with a known allergen exposure is anaphylaxis until proven otherwise. If in doubt, treat.
What Not to Do
Antihistamines (cetirizine, chlorphenamine) treat hives. They do not treat anaphylaxis. They work too slowly, do nothing for the airway, and do nothing for cardiovascular collapse. Giving an antihistamine instead of adrenaline wastes time that you do not have.
Oral steroids also work too slowly for the acute phase. They are sometimes given in hospital to reduce biphasic reaction risk but are not part of the immediate response.
Do not have the child stand or sit upright if they are feeling faint — lie them flat with legs raised. The exception is a child whose breathing is so difficult they need to sit up; in that case, sit them up and brace them. Sudden standing or sitting after a flat collapse can cause a dangerous drop in blood pressure ("empty heart syndrome") — there have been recorded fatalities from this alone.
Using an Adrenaline Auto-Injector
Three auto-injector brands are available in the UK: EpiPen, Emerade, and Jext. Dosing per Resuscitation Council UK:
- 150 microgram device (EpiPen Jr, Jext 150, Emerade 150): for children weighing 7.5-25 kg, roughly age 1 to 6.
- 300 microgram device (EpiPen, Jext 300, Emerade 300): for children over 25 kg.
- 500 microgram Emerade is also available for older children and adults.
Technique varies slightly between brands; families should be trained on the device they have been prescribed. Universal principles:
- Remove the safety cap.
- Hold the device firmly with the tip pointing down at the outer mid-thigh — halfway between hip and knee, on the outside of the leg.
- Jab firmly into the outer mid-thigh. Through clothing is fine — denim, leggings, school trousers all work.
- Hold in place for 10 seconds (count out loud).
- Remove and massage the site briefly.
Call 999 immediately before or right after injecting and tell the operator the word "anaphylaxis." Do not wait to see if the first dose works before calling. If symptoms do not improve or worsen 5 minutes after the first dose, give the second auto-injector. This is why two devices must always be carried.
After any auto-injector use, the child must go to hospital by ambulance even if they appear to have recovered completely. Biphasic reactions — a second wave of anaphylaxis hours after the first — occur in up to 20% of cases. UK practice is hospital observation for 4-6 hours after a moderate reaction, longer if severe.
Allergy Action Plans
Every child prescribed an auto-injector should have a personalised allergy action plan from their allergy team, listing their known allergens, what symptoms to treat with antihistamine, what symptoms require adrenaline, and when to call 999. Share copies with the school, childminder, after-school clubs, and any regular caregiver. Schools have a duty under the Children and Families Act 2014 to support children with medical conditions.
Anaphylaxis UK (anaphylaxis.org.uk) and the BSACI both publish template plans, training resources, and a free helpline.
Key Takeaways
Anaphylaxis is a severe, life-threatening allergic reaction needing immediate intramuscular adrenaline. The most common triggers in UK children are foods (peanut, tree nuts, milk, egg, fish, sesame), insect stings, and medications. The defining feature is sudden involvement of two or more body systems — typically skin plus airway, breathing, or circulation — within minutes to two hours of exposure. Antihistamines treat hives but do not treat anaphylaxis and must not delay adrenaline. Auto-injector dosing (Resuscitation Council UK): EpiPen Jr / Jext 150 / Emerade 150 (150 micrograms) for children 7.5-25 kg; EpiPen / Jext 300 / Emerade 300 or 500 (300 micrograms) for children over 25 kg. Inject into the outer mid-thigh, hold for 10 seconds, call 999, and always carry two devices. Hospital observation is standard after any use because biphasic reactions can occur up to 8 hours later.
