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Signs of an allergic reaction in babies

Hives, vomiting, swelling: what to watch for after a new food, and exactly when to call for help.

verifiedReviewed by our dietitians

Parent spoon-feeding a baby in a high chair on a bright morning and watching closely

Quick answer

Most food allergic reactions start within minutes to 2 hours of eating. Common signs are hives, swelling of the face or lips, and vomiting. Call 911 right away if baby has any trouble breathing, wheezing, repeated coughing, swelling of the tongue or throat, widespread hives, repeated vomiting, or becomes pale, floppy or unusually sleepy: these can be signs of anaphylaxis. A few hives around the mouth with no other symptoms is mild: stop the food and call your pediatrician.

Most reactions start within minutes to 2 hours of eating
Breathing trouble, swelling, repeated vomiting or floppiness: call 911
A few hives only: stop the food and call your pediatrician

STEP 1

When should I call 911 for an allergic reaction?

Call 911 (or your local emergency number) if baby has ANY of these Trouble breathing, wheezing, noisy or high-pitched breathing • Repeated coughing or a hoarse cry • Swelling of the tongue, lips or face • Hives spreading over the body • Repeated vomiting • Pale or blue skin • Floppiness, sudden sleepiness or not responding.

1If baby has a prescribed epinephrine auto-injector, use it now. Don’t wait to see if symptoms improve.
2Call 911 and say “my baby is having an allergic reaction”.
3Lay baby flat on their back. If they are vomiting, turn them on their side. Don’t hold them upright or let them walk if they are floppy.
4Stay with baby. A second dose of epinephrine may be needed after 5 minutes if symptoms don’t improve and you have one.

Antihistamines do not stop anaphylaxis. Never use one instead of epinephrine or a 911 call.

STEP 2

Mild vs severe allergic reaction symptoms

Mild

A few hives or red, raised welts around the mouth or face. Mild itchy skin. One episode of vomiting with baby otherwise well. Stop the food and call your pediatrician.

Severe (anaphylaxis)

Symptoms in more than one body system, or any breathing trouble, throat or tongue swelling, repeated vomiting, or floppiness. Call 911 and use epinephrine if prescribed.

Babies can’t tell you their throat feels tight. In infants, the signs of a serious reaction can be sudden sleepiness, floppiness, drooling, persistent crying or scratching at the tongue or ears.

STEP 3

Is it an allergy or just a contact rash?

Acidic foods like tomato, strawberries and citrus often leave red, blotchy skin around the mouth where the food touched. This is a contact rash, not an allergy.

Likely contact rash

Flat redness only where food touched, no swelling, baby happy, fades within an hour after wiping the skin.

Possible allergy

Raised hives that spread beyond where food touched, swelling, vomiting, or any change in breathing or behavior.

Not sure? Take a photo and call your pediatrician.

STEP 4

Can allergic reactions be delayed?

Yes. Some food reactions don’t show up for hours:

FPIES (food protein-induced enterocolitis syndrome): repeated, heavy vomiting 1 to 4 hours after eating, often with paleness, floppiness and later diarrhea. Common triggers are oats, rice, egg, milk, soy and fish. Seek medical care the same day; call 911 if baby is very floppy or hard to wake.
Blood or mucus in stool over days, often linked to milk protein (FPIAP). Call your pediatrician.
Eczema flares hours to days after a food. Keep a log and talk to your pediatrician before cutting foods.

STEP 5

What to write down after a reaction

Notebook, pen and phone beside a bowl of fully cooked scrambled egg, ready to log a new food

A simple record helps your pediatrician or allergist work out what happened. Write it down while it is fresh, and take photos before symptoms fade.

The food, the brand and how it was prepared (raw, cooked, baked)
Roughly how much baby ate, and whether it was the first time
What time baby ate, and what time each symptom started
Exactly what you saw: where the hives were, how many times baby vomited
What you did, and how long until symptoms settled
Anything else going on: a cold, a new soap, teething, an eczema flare

Your allergen plan log can hold most of this. Bring it, and your photos, to the appointment.

STEP 6

What to do after a mild reaction

1Stop the food and gently wipe baby’s face and hands.
2Take photos of the skin and note the time, food and amount.
3Watch baby closely for at least 2 hours for any severe signs.
4Call your pediatrician. Ask before giving any antihistamine; they will tell you whether to use one and the right dose for baby’s weight.
5Don’t serve that food again until a doctor says so. You may be referred to an allergist.

STEP 7

How to introduce allergens safely

Introduce one new allergen at a time, a few days apart
Serve new allergens at home, early in the day, when baby is healthy
Start with a small amount, wait 10 minutes, then offer more
Once an allergen is in, keep it in regularly

Step-by-step guides: peanut and egg, or follow the Top 9 allergen plan.

AVOID THESE

Common mistakes to avoid

Waiting to see if a severe reaction gets better before calling 911
Giving an antihistamine instead of epinephrine for a severe reaction
Holding a floppy baby upright during a reaction
Mistaking a flat contact rash from tomato or berries for an allergy and dropping the food
Introducing two new allergens on the same day
Re-offering a food that caused hives before talking to your pediatrician

GET HELP

When to call your pediatrician or allergist

Not every reaction is an emergency, but every reaction deserves a call. Phone your pediatrician the same day if baby has:

A few hives or welts that settle on their own
Vomiting once after a new food, then seems well
Repeated vomiting 1 to 4 hours after a food (possible FPIES)
An eczema flare that seems linked to a food
Blood or mucus in the stool
Any reaction to peanut, egg, milk or another allergen you plan to keep serving

Call emergency services (911 in the US) instead if there is any breathing trouble, swelling of the tongue or throat, widespread hives, repeated vomiting with other symptoms, or floppiness.

Allergic reactions in babies: questions parents ask

What does an allergic reaction look like in a baby?

The most common signs are hives (raised, red, itchy welts), swelling around the lips, eyes or face, and vomiting. Serious reactions can include wheezing, coughing, trouble breathing, a hoarse cry, and sudden sleepiness or floppiness.

How long after eating does an allergic reaction happen?

Most food allergic reactions start within minutes to 2 hours after eating. Delayed reactions such as FPIES cause repeated vomiting 1 to 4 hours later.

When should I call 911 for my baby’s allergic reaction?

Call 911 for any breathing trouble, wheezing, repeated coughing, swelling of the tongue or throat, widespread hives, repeated vomiting, pale or blue skin, or floppiness or unusual sleepiness. Use an epinephrine auto-injector first if one has been prescribed.

Can I give my baby Benadryl for an allergic reaction?

Only if your pediatrician tells you to and gives you a dose for your baby. Antihistamines can ease mild hives but do not treat anaphylaxis. For a severe reaction, call 911 and use epinephrine if prescribed.

Is a rash around the mouth an allergic reaction?

Not always. Acidic foods like tomato, berries and citrus often cause a flat, red contact rash where the food touched. It fades within an hour and baby stays well. Raised hives that spread, swelling or vomiting suggest an allergy.

What are the most common food allergies in babies?

The most common are cow’s milk, egg and peanut, followed by tree nuts, sesame, soy, wheat, fish and shellfish. Together with these, they make up the Top 9 allergens in the US.

What is FPIES?

FPIES is a delayed food allergy that affects the gut. It causes repeated, heavy vomiting 1 to 4 hours after eating a trigger food, often with paleness and floppiness. It does not cause hives or breathing trouble. Seek medical care the same day.

Should I wait 3 days between new foods?

For the major allergens, it helps to introduce one at a time and wait a few days before the next new allergen, so you can tell what caused a reaction. Non-allergenic foods like most fruits and vegetables don’t need a waiting period.

Can a baby react to a food they have eaten before?

Yes. A reaction can happen the second or third time a food is eaten. That is one more reason to keep allergens in the diet regularly and to keep watching for symptoms.

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Sources

This guide is written for healthy, full-term babies and doesn’t replace your pediatrician. If your baby was born early, has a medical condition, feeding or swallowing difficulties, or a known allergy, check with them first (medical disclaimer). Reviewed by our dietitians.