Quick answer: Knowing how to identify and respond to an allergic reaction in your baby could save their life.
Knowing how to identify and respond to an allergic reaction in your baby could save their life. Allergic reactions range from mild to anaphylactic — and every parent needs to know the difference.
Types of Allergic Reactions
Mild-moderate reaction: Hives (urticaria) — raised, itchy welts on the skin that appear and may spread. Facial swelling — around the eyes and lips. Runny nose, watery eyes. Eczema flare. Vomiting within 2 hours of eating. These don’t threaten the airway or circulation and don’t require epinephrine. Anaphylaxis: A severe, life-threatening allergic reaction involving two or more body systems: skin reactions (hives, flushing) PLUS either respiratory symptoms (wheeze, difficulty breathing, stridor) or cardiovascular symptoms (drop in blood pressure, collapse, loss of consciousness, extreme pallor). Signs in babies: sudden difficulty breathing, wheezing, hoarse cry, vomiting with hives, extreme pallor, limpness, loss of consciousness. Anaphylaxis requires immediate epinephrine (EpiPen) and emergency care.
Common Allergens in Babies
- Cow’s milk — the most common food allergen in infancy
- Egg — particularly egg white
- Peanut — affects 1–2% of children
- Tree nuts (cashew, walnut, almond)
- Fish and shellfish
- Wheat
- Soy
- Insect stings (bees, wasps)
Immediate Response to Mild-Moderate Reaction
For hives or mild facial swelling without airway or breathing involvement: remove the trigger (stop feeding, remove the food). Oral antihistamine (loratadine or cetirizine are appropriate for babies over 6 months; chlorphenamine/Piriton is also used but more sedating). Monitor closely for 2–4 hours. Contact your GP the same day to discuss allergy testing and management plan. Do not give a second exposure to the suspected food without an allergy assessment.
Responding to Anaphylaxis
Call 999/911 immediately. If the child has a prescribed epinephrine auto-injector (EpiPen Jr): use it immediately in the outer thigh (through clothing is fine). Lay child flat with legs raised (unless breathing is easier sitting up). Give a second epinephrine dose if symptoms don’t improve after 5–10 minutes and you have a second device. Do not give antihistamines alone for anaphylaxis — they work too slowly and don’t address the airway or cardiovascular components. Antihistamines are adjuncts after epinephrine.
After an Allergic Reaction: Next Steps
Any child who has had a suspected allergic reaction to food should be referred to a paediatric allergy service for: skin prick testing or specific IgE blood tests to confirm the allergy, allergy action plan, and EpiPen prescription if at risk of anaphylaxis. Don’t try to reintroduce the suspected food at home before allergy assessment — the second reaction can be more severe than the first.
Frequently Asked Questions
Should I introduce allergens early to prevent allergy?
Yes — current guidelines from LEAP study onwards recommend early introduction of common allergens (peanut, egg) from around 6 months (when solid foods begin), in babies who are already eating some solids. Early introduction significantly reduces allergy development. For babies with severe eczema or existing egg allergy, discuss with a GP or allergist before introducing peanut.
How long after eating does an allergic reaction happen?
IgE-mediated (immediate) reactions occur within minutes to 2 hours of ingestion. Non-IgE-mediated (delayed) reactions occur hours to days later. The immediate reactions are the ones causing hives, swelling, and anaphylaxis. Delayed reactions more commonly cause eczema, GI symptoms, and are more difficult to identify.
My baby had hives once after eating — are they allergic forever?
Not necessarily. Many children outgrow food allergies, particularly to milk and egg (most outgrow by school age). Peanut and tree nut allergies are more persistent. A formal allergy assessment and regular review (annual if under 5, as many outgrow allergies) determines whether allergy persists and when safe reintroduction can be attempted.
Related Reading
- How to introduce allergens to babies
- Rashes in babies: a visual guide to common skin conditions
- Eczema in babies: causes, triggers and treatment
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