Severe Allergic Reactions in Babies: Recognizing Anaphylaxis and Introducing Allergens Safely
A baby can’t tell you their throat feels tight. Learn to read the signs of a serious reaction, what to do in an emergency, and how to introduce allergens the way today’s guidance recommends.
If a baby shows any sign of a severe allergic reaction (anaphylaxis) — trouble breathing, swelling of the lips, tongue, or throat, a hoarse cry, floppiness, or drowsiness after a food: (1) give a prescribed epinephrine auto-injector into the outer thigh right away — it’s the first-line treatment; (2) call 911; (3) lay the baby down (or upright if they’re struggling to breathe) and stay with them; (4) if there’s no improvement about 5 minutes later and a second device is available, give a second dose. Always go to hospital, even if the baby recovers. For a few hives only, stop the food, keep the baby calm, and call your doctor.
This Article Is About Allergies, Not Choking
It is worth saying clearly: an allergic reaction and choking are different emergencies that can look similar (both can cause breathing trouble), but they need different responses. If a baby was eating and suddenly cannot breathe, cry, or cough and is silent, treat it as choking — for a baby that means 5 back blows and 5 chest thrusts, never abdominal thrusts. If breathing trouble comes with hives, swelling, or vomiting after a food, treat it as an allergic reaction. A hands-on first aid course teaches you to tell them apart quickly.
Recognizing an Allergic Reaction in a Baby
Because babies cannot describe how they feel, you have to read their skin, breathing, and behaviour. Reactions usually appear within minutes to two hours of eating the food. A useful rule from the Canadian Red Cross: treat it as anaphylaxis when signs affect two or more body systems — for example skin (hives) plus breathing, or breathing plus circulation (floppiness, collapse).
Source: Canadian Red Cross 2025; ILCOR 2025 first aid consensus (FA 7110, recognition of anaphylaxis).
Mild to moderate signs
- Hives — raised, red, itchy welts, often around the mouth first, then elsewhere
- Redness or flushing of the skin
- Swelling around the lips, eyes, or face
- Vomiting or sudden tummy upset
- Itchiness — a baby may rub their face, ears, or tongue, or become suddenly fussy
Severe signs (anaphylaxis) — a 911 emergency
- Swelling of the tongue or throat, or a sense the airway is closing
- Noisy, difficult, or very fast breathing; persistent cough or wheeze
- A hoarse, weak, or strange-sounding cry
- Pale, blue-tinged, or floppy appearance
- Sudden drowsiness, limpness, or unresponsiveness
- Repeated vomiting with other symptoms, or collapse
Step-by-Step: Responding to an Allergic Emergency
1Stop the food and assess
Remove any remaining food from your baby’s mouth and hands. Quickly check: is this just a few hives, or are breathing and alertness affected? That distinction decides what you do next.
2For a mild reaction, call your doctor
If it is limited to a few hives or mild swelling with no breathing trouble, keep your baby calm and contact your doctor or a nurse line for advice. They may recommend an infant antihistamine and will want to know about the reaction. Watch your baby closely for at least a couple of hours, as symptoms can progress.
3For any severe sign, call 911 immediately
Do not wait to “see how it goes.” Call 911 the moment you see breathing difficulty, throat or tongue swelling, a hoarse cry, floppiness, or drowsiness. If someone is with you, give the epinephrine (next step) while they call.
4Give the epinephrine auto-injector first — don’t wait
If your baby has been prescribed an epinephrine auto-injector for a known allergy, give it first and without hesitation, intramuscularly into the outer thigh, following the device instructions. Epinephrine is the first-line treatment for anaphylaxis — it reverses the reaction, works fast, and is safe. Do not reach for an antihistamine instead; it acts too slowly to hold back a severe reaction. Hesitation is far more dangerous than giving epinephrine.
Source: ILCOR 2025 first aid consensus (FA 7111); Canadian Red Cross 2025 / AHA 2024 (IM epinephrine, outer thigh, first-line).
5Position your baby and repeat epinephrine if needed
If your baby is struggling to breathe, hold them upright against you. If they are floppy or faint, lay them down. Stay calm and keep them comfortable while you wait for paramedics. If there is no improvement about 5 minutes after the first dose and a second device is available, give a second dose of epinephrine.
Source: ILCOR 2025 (FA 7111, second dose if symptoms not relieved); ERC 2025 First Aid / Canadian Red Cross (recheck at ~5 minutes).
6If your baby becomes unresponsive and stops breathing — begin infant CPR
Start infant CPR immediately and continue until help arrives — use the two-thumb encircling technique or the heel of one hand on the lower half of the breastbone. See our Baby CPR guide, and consider taking a hands-on course so the technique is second nature.
Source: Canadian Red Cross 2025; Heart & Stroke Foundation (ILCOR 2025 BLS).
Introducing Allergens Safely: What Today’s Guidance Says
For years, parents were told to delay allergenic foods. That advice has reversed. Current Canadian guidance — from Health Canada, the Canadian Paediatric Society, and Canadian allergy societies — recommends introducing common allergens around 6 months, when your baby is developmentally ready for solids, and continuing to offer them regularly. Landmark trials (such as the LEAP study on peanut) have shown that early, sustained introduction can meaningfully reduce the chance of developing allergies, especially to peanut and egg.
Source: Health Canada / Canadian Paediatric Society infant feeding guidance; Canadian Society of Allergy and Clinical Immunology (CSACI) early-introduction statements.
The most common food allergens to introduce include: peanut, egg, dairy (cow’s milk), wheat, soy, tree nuts, sesame, fish, and shellfish.
How to do it safely
- Make sure your baby is ready for solids — usually around 6 months, able to sit with support and showing interest in food.
- Introduce one new allergen at a time, a few days apart, so you can identify the culprit if a reaction occurs.
- Offer it earlier in the day and at home — not right before bed and not the first time at daycare — so you can watch for a reaction over the following hours.
- Start with a small amount, wait a few minutes, and if there is no reaction, continue with a little more.
- Keep offering it regularly once tolerated — roughly a couple of times a week — since ongoing exposure helps maintain tolerance.
- Use safe textures to avoid choking (see below).
When to talk to your doctor first
Speak with your doctor or an allergist before introducing allergens if your baby has severe eczema, an existing food allergy (for example, an egg allergy before introducing peanut), or a strong family history of allergies. These babies are at higher risk and may benefit from allergy testing or supervised introduction.
Know the Signs, Practise the Response
Reading about anaphylaxis is important — but in the moment, parents need calm, practised hands. A Life Safe infant first aid course covers allergic reactions, epinephrine auto-injector technique, the difference between choking and anaphylaxis, and infant CPR, all with hands-on practice. It is the kind of preparation that turns one of parenting’s scariest moments into something you can handle.
Frequently Asked Questions
How can I tell if my baby is having a severe allergic reaction?
Watch their body and behaviour. Mild signs include hives, redness, facial swelling, and vomiting. Severe signs (anaphylaxis) include swelling of the lips, tongue, or throat, noisy or difficult breathing, persistent cough or wheeze, a hoarse cry, pale or floppy appearance, sudden drowsiness, and collapse. Per the Canadian Red Cross, act when signs affect two or more body systems (for example skin plus breathing). Any breathing trouble or floppiness is an emergency — call 911 and use epinephrine if prescribed.
When should I introduce allergens to my baby?
Current Canadian guidance (Health Canada and the Canadian Paediatric Society) is to introduce common allergens like peanut, egg, and dairy around 6 months, when your baby is ready for solids, and not to delay. Early, regular introduction can reduce the risk of developing a food allergy. Offer one allergen at a time in a safe texture, and talk to your doctor first if your baby has severe eczema or an existing food allergy.
How do I safely give my baby peanut for the first time?
Never give whole peanuts or thick globs of peanut butter — they are choking hazards. Mix a small amount of smooth peanut butter into warm water, breast milk, or puree to thin it. Offer it earlier in the day, at home, so you can watch your baby for several hours. Start with a tiny taste, wait, then continue. Speak to your doctor first if your baby has severe eczema or an egg allergy.
What do I do if my baby has an allergic reaction to food?
For a mild reaction like a few hives, stop the food, keep your baby calm, and call your doctor for advice. For any severe sign — breathing trouble, tongue or throat swelling, a hoarse cry, floppiness, or collapse — give a prescribed epinephrine auto-injector into the outer thigh first, then call 911. Epinephrine is the first-line treatment; never hesitate in a true emergency. If there’s no relief and a second device is available, a second dose can be given about 5 minutes later.
Feel Confident Introducing Solids
Knowing how to recognize and respond to an allergic reaction takes the fear out of your baby’s first foods. Life Safe’s hands-on infant first aid courses cover anaphylaxis, auto-injectors, choking, and CPR so you are ready for whatever the high chair brings.
Find a class near you: Toronto • Downtown Toronto • East York • Hamilton • Welland • Guelph
Sources & medical review
Reviewed by Milos Radojcic (Canadian Red Cross / Heart & Stroke / Lifesaving Society First Aid & CPR Instructor, 10+ yrs). Clinical content aligned with the Canadian Red Cross (2025), the Heart & Stroke Foundation of Canada, and the 2025 ILCOR first aid consensus (FA 7110 recognition; FA 7111 epinephrine and second dose). Allergen-introduction guidance from Health Canada, the Canadian Paediatric Society, and the Canadian Society of Allergy and Clinical Immunology (CSACI). Last reviewed July 2026.