Allergy Symptoms in Babies

Symptoms of Food Allergies in Babies

Symptoms vary and range from mild to severe. Generally, the severity of a reaction is judged by how many symptoms are present and the severity of those symptoms. 

If you think baby is having an allergic reaction, call emergency services immediately.

Symptoms of Allergic Reaction in Babies

Mild Reaction

Includes ONE of the following (more than one is a severe reaction):

A mild allergic reaction involves one symptom. For example, baby might have a few isolated hives around the mouth, a runny nose, or a single episode of vomiting. If you see only one of these, stop feeding the allergen and contact your doctor or allergist for guidance.

If baby is having multiple symptoms, call emergency services immediately and request an ambulance equipped with epinephrine.

Severe Reaction 

Includes any of the following, either alone or in combination:

A severe allergic reaction is called anaphylaxis. It involves two or more body systems at the same time, or includes any severe symptom on its own. It can progress rapidly, which is why immediate action is essential.

If baby is having any of the above symptoms, call emergency services immediately and request an ambulance equipped with epinephrine. Do not wait.

The distinction families most commonly miss: anaphylaxis does not always look dramatic at the outset. A baby who develops hives and then vomits, or who seems unusually floppy and is also coughing, is showing signs affecting more than one body system—even if no single symptom appears severe on its own. When more than one system is involved, call emergency services right away.

Delayed Reactions

Most allergic reactions occur within minutes of eating, though delayed reactions that occur several hours later are possible with FPIES, an increasingly recognized food allergy in babies and young children. It is often challenging to confirm an FPIES allergic reaction without the support of your doctor and a pediatric allergist or gastroenterologist because the most common symptoms are vomiting and diarrhea, which are common reactions to a number of childhood illnesses. Check out FPIES in Babies for more information. 

A baby may not have an allergic reaction the first time they are exposed to the food, so be watchful on the second and the first few subsequent exposures. Generally, the more of the allergen consumed, the more severe the reaction is likely to be, so it is important to start small when introducing new foods and gradually work up to larger quantities served at mealtime. 

Why Anaphylaxis Looks Different in Babies

Older kids can tell you when something feels wrong. They might say their throat feels tight or their heart is beating fast. Babies can't talk yet, so you have to watch for other signs. Look at their skin, their breathing, how their body moves, and how they're acting.

Early signs of a bad allergic reaction in babies can include fussiness, tiredness, or an upset stomach. The tricky part is that babies often act this way even when nothing is wrong. Pay close attention to timing: if these signs show up soon after your baby eats something, take it seriously.

It also helps to know what to look for before you introduce a new food. Many parents and caregivers don't realize baby is having a reaction until after it's over. Learning the symptoms of an allergic reaction ahead of time makes them much easier to spot.

Anaphylaxis in Infants vs. Toddlers

The Asthma and Allergy Foundation of America studied severe allergic reactions in children under three. They talked to parents and caregivers who had watched their baby or toddler go through a severe allergic reaction.

Key findings include: 

The study also found that the guidelines doctors and caregivers typically use to recognize anaphylaxis were written with older children and adults in mind—not babies. This matters because anaphylaxis can look different in infants than it does in older kids. On top of that, some symptoms of anaphylaxis in babies (like fussiness or vomiting) can also be signs of common illnesses in babies, which makes them easy to miss.

Common Triggers of Allergic Reactions in Babies

Food Allergens

For babies under 12 months of age, egg and cow's milk are the most common food allergens, followed by peanut, sesame, wheat, and tree nuts like almond, cashew, hazelnut, and pecan. While food is the most common trigger of food allergens in babies, most babies and toddlers do not have food allergies, and will never experience an allergic reaction. You can help prevent food allergies from developing by safely introducing allergens early on when starting solids and regularly keeping them in the diet. 

For babies who are allergic to a food, a severe allergic reaction (anaphylaxis) is very unlikely the very first time they taste the food allergen. That's because the body's immune system needs to encounter the food at least once before it can build up a strong enough reaction to cause a dangerous response. However, small, unnoticed exposures—like repeated skin exposure to the allergen residue from the hands of a caregiver (especially if baby has eczema), can silently make the immune system more sensitive over time. This is why a severe reaction can sometimes seem to come out of nowhere.

Medications

Certain medications can trigger allergic reactions in babies. Penicillin-based antibiotics—including amoxicillin, one of the most commonly prescribed antibiotics in early childhood—are among the most recognized medication triggers. If baby is being prescribed an antibiotic for the first time, get familiar with the symptoms of an allergic reaction and pay close attention after the first few doses. Allergic reactions to medications typically appear within the first few doses, not when the course of medication is nearly complete. Keep in mind that most rashes that appear while a baby is on an antibiotic are related to the illness itself, and not due to a drug allergy.

Insect Stings and Latex

Insect stings (such as bees, hornets, wasps, yellow jackets, and fire ants) and latex are less common triggers of allergic reactions in infants than food or medications, but both are recognized causes. Babies with a known latex allergy may need to avoid latex-containing medical equipment, like latex gloves, rubber catheters, or certain bandages.

Critical info for caregivers

Should you or your caregivers need to call emergency services, things will move more quickly if you have the following information readily available. Enter it in your own phone and post it on your refrigerator for caregivers.

Eczema Flare-up vs. Allergic Reaction vs. Contact Rash

An eczema flare-up, an allergic reaction, and a contact rash can all involve itchy, inflamed skin, which can confuse parents on what to do next. Yet knowing the difference between them can help you respond quickly if needed, or can prevent an unnecessary elimination of food from your child’s diet which can sometimes increase the risk of an allergy developing, rather than reduce it. So how can you tell the difference? 

Start by examining the skin: if the rash is widespread (such as all over the torso, arms, and legs), it is more likely to be an allergic reaction and you should seek immediate medical guidance, especially if there are other symptoms of an allergic reaction. If you are not sure, it is always reasonable to seek medical guidance rather than waiting. 

What's The Difference? Eczema vs. Allergy vs. Contact Rash 

* For IgE-mediated allergies. Symptoms of allergic reactions vary depending on the type of allergy. Check out FPIES in Babies for symptoms of delayed allergic reaction, which are less common.  

An eczema flare-up usually develops more slowly and tends to show up in areas where the skin is already sensitive, such as the creases of the elbows or knees, wrists, ankles, neck, or cheeks, and the skin often looks dry, rough, or scaly and may thicken over time from scratching. The flare can last days to weeks and is often triggered by things like dry air, sweating, stress, illness, or irritating soaps rather than a single allergen exposure. 

An allergic reaction to food usually appears suddenly (within minutes to hours after contact with an allergenic food) and often causes raised, smooth, itchy bumps (hives) or swelling that can move around the body and fade within hours. Allergic reactions are also more likely to come with other symptoms, such as lip or eyelid swelling, vomiting, coughing, or trouble breathing, which are not features of eczema.

Contact rashes from acidic foods (such as lemon, orange, pineapple, and tomato) usually show up in a limited area where your baby’s skin came in contact with food, such as around the mouth and on the chin. Contact rashes typically dissipate within 10 minutes of a gentle cleanse, and there tend to be no other symptoms. If the rash does not resolve quickly after gentle cleansing, call your doctor for guidance. There is a chance that the reaction might become more serious if left untreated. 

When in doubt, discuss with your baby’s healthcare provider. To offer them the most information possible, make sure to document the following information: 

What to Do If Baby Shows Signs of A Severe Reaction

Step 1: Give Epinephrine First and Fast

Early use of epinephrine is one of the most important factors in preventing a reaction from becoming life-threatening. Delaying or failing to use epinephrine can make things worse. 

If epinephrine has been prescribed for baby, give it immediately at the first sign of suspected anaphylaxis—do not wait for symptoms to worsen. 

If you suspect anaphylaxis but don’t have epinephrine available, call emergency services right away and request an ambulance with epinephrine on board. 

If you are not certain whether what you are seeing is anaphylaxis, it is okay to give the epinephrine anyway. The risk of giving epinephrine when it was not strictly needed is far smaller than the risk of withholding it during a true reaction.

Step 2: How to Administer an EpiPen

If baby is at risk of anaphylaxis and has been prescribed epinephrine, your doctor will explain how to use the specific epinephrine device that has been prescribed. Make sure every caregiver who spends time with baby is familiar with your prescribed device.

General steps for most auto-injectors:

For babies and toddlers who weigh less than 33 lbs (15 kg), either the 0.1 mg or the 0.15 mg epinephrine auto-injector dose may be appropriate. Your doctor will advise which has been prescribed and why. 

Step 3: Call Emergency Services

Call emergency services immediately if epinephrine is not available, or if baby's symptoms are not improving after the first dose of epinephrine. Do not wait to see if things get better on their own.

If baby's symptoms resolve quickly and completely after epinephrine, current guidance allows for home observation in some situations—but for babies, this decision requires extra caution. Because baby cannot tell you how they feel, and because some serious signs can be subtle or appear after an initial recovery, the safest choice when you are unsure is always to call emergency services.

Call emergency services right away if:

You may watch closely at home while staying ready to call emergency services if: 

Even when baby appears to have fully recovered, a second wave of symptoms—called a biphasic reaction—can occur hours later. See Step 5 for more on this.

Step 4. Position Baby for Safety

Unless baby is having trouble breathing, lay them on their back with legs elevated. 

If baby is having difficulty breathing, keep them in the position that makes breathing easiest,  usually semi-upright. 

If baby loses consciousness, place them on their side. Never leave baby unattended.

Step 5: Watch for A Second Wave

A biphasic reaction is a second wave of anaphylaxis symptoms that can occur up to 72 hours after the initial reaction has resolved—without any further allergen exposure. However, the vast majority of biphasic reactions appear within the first 8 hours after anaphylaxis has resolved. Biphasic reactions are unpredictable and can range from mild to severe.

This is one of the key reasons why emergency department evaluation is recommended after an anaphylactic reaction, particularly when symptoms were severe or did not resolve quickly after a single dose of epinephrine.

Always have two epinephrine auto-injectors available. If symptoms return or do not fully resolve after the first dose, a second dose may be needed.

Step 6: Follow-Up After a Reaction

After any episode of anaphylaxis, follow-up with a board-certified allergist is important. 

Your allergist can:

Why An Anaphylaxis Action Plan Saves Lives

An Allergy and Anaphylaxis Emergency Care Plan is a written document, prepared with your allergist, that specifies which allergens to avoid, which symptoms require epinephrine, how to use the auto-injector, and when to call emergency services. 

Every caregiver who spends time with baby— family members, caregivers, nursery staff—should have access to a copy of your plan and know how to follow it.

Research shows that children with a diagnosed food allergy who had an emergency care plan in place were significantly more likely to receive epinephrine during a severe reaction than those without one. When seconds matter, a clear written plan removes hesitation.