Understanding and Diagnosing Food Allergies in Infants & Toddlers

Introducing your baby to new foods is an exciting stage of their life. While many babies eat new foods without any issues, sometimes you may notice odd reactions after they try a certain food. When these symptoms happen, it may be time to find out whether a food allergy is involved.

This page will help you:

Understand what an IgE-mediated food allergy is and how it’s diagnosed
Learn about common allergy tests and what they look like for your baby
Understand non-IgE-mediated food allergies and what these mean for your baby
Prepare for appointments and conversations with your child’s allergist
Navigate what comes next after a diagnosis

A young child with blond hair and blue eyes smiles with an open mouth as an adult hand feeds them with a blue spoon. The background is softly blurred.

This guide is here to support you with easy-to-understand, medically reviewed food allergy and anaphylaxis information you can trust. Use this as a resource as you prepare to talk with your child’s healthcare team.

What is a food allergy?

Your baby’s immune system is still developing and learning what is safe. Sometimes, when babies try new foods, their immune system can overreact and treat them as harmful invaders. This is called a food allergy.

“True” food allergies are also called IgE-mediated food allergies. IgE is an antibody that your immune system makes to fight off allergens that it thinks are harmful. In some people, certain foods can make IgE overreact and release a bunch of chemicals, which cause the symptoms you see during a reaction.

Reactions usually happen quickly—within minutes to a few hours after eating. Severe reactions can be life-threatening and require emergency treatment, but they are fortunately rare in babies.

In most cases, symptoms are mild. Common signs can include:

itchy eyes or nose
coughing or sneezing
more drool or spit-up than usual
fussiness
hives

If your baby has mild symptoms after eating, this is something to bring up with your child’s doctor. They can help you decide if allergy testing is needed.

Best medical tests for finding allergies

Diagnosing a food allergy is often a step-by-step process, and there isn’t a single test that gives all the answers. Sometimes, a test may come back positive even if your baby doesn’t actually have a food allergy. To make the most accurate diagnosis, your child’s doctor will look at the whole picture: your observations, your baby’s medical history, and carefully chosen tests.

What may your doctor ask you? Before or during the appointment, be ready to share:

What foods your baby has eaten
What symptoms you noticed
How long after eating the symptoms started
Whether your baby has eaten the food before without any problems
Any history of eczema or allergies

Writing this information down ahead of time can make it easier to remember details during the appointment. If possible, bring photos of any rashes, swelling, or other visible reactions.

There are two main food allergy tests: skin prick testing and specific IgE blood tests.

Common allergy tests

Testing for food allergies doesn’t have to be scary. When done under the supervision of a trained doctor, these tests are very safe—even for babies. This section will explain what happens during each test and what you and your baby can expect.

What happens: A small drop of liquid that contains the food protein is placed on your baby’s skin. Then the skin is gently pricked so the liquid can get inside. You’ll usually wait about 15-20 minutes while the doctor looks for a reaction.

What to expect: If your baby has a reaction, a small red bump (like a mosquito bite) will appear where the skin was pricked. This bump is called a wheal. The doctor will measure the size of the wheal which can help show how likely it is that your child has an allergy.

What happens: A small blood sample is taken from your baby’s arm using a thin needle. Your baby will feel a quick pinch, and the process only takes a few minutes. There may be a little bruising or soreness after which usually goes away quickly.

What to expect: The blood is sent to a lab to measure food-specific IgE levels. Higher numbers may suggest an allergy, but the results do not tell the doctor exactly which food causes a reaction or how severe it might be. It usually takes a few days for results to come back from the lab.

Special diagnosing methods

Sometimes, skin prick and blood tests do not give clear enough answers. So an allergist may use other methods to find out if a baby truly has a food allergy, or, you may read about other types of tests and have questions for your healthcare team.

Foods are made up of many proteins. A component test takes a blood sample and checks for these proteins, specifically IgE antibodies, against specific parts of a food. For example, some babies react to proteins in raw eggs but can safely eat baked eggs. A component test tells the allergist which parts of the food cause a reaction.

Before the challenge: Your allergist will give you specific instructions to follow to prepare for the test, but if anything is unclear, you can ask questions like:

Do I need to stop giving any of my child’s medications?
Can they eat anything before the test?
Do I need to bring the food for the test, or will it be provided?
Do I need to bring my own epinephrine?
Should we still come in if my child is sick today?

What happens: Your child will eat small amounts of the food being tested while your allergist and their team watch closely for any signs of an allergic reaction. If there are no symptoms, your child will try slightly larger amounts. If any symptoms do occur, your allergist will decide whether to stop the test and will have emergency medication ready just in case. The whole challenge usually takes a few hours so your child can be monitored safely after they finish eating.

What to expect: If your child has no reaction, they are likely not allergic to the food. If symptoms do appear, your allergist will review the results with you and discuss next steps.

If the baby shows allergy symptoms after eating the food, the baby has that food allergy.
If the baby has no reaction, the baby is not allergic to that food.

Oral food challenges should always be conducted in a clinic or hospital. Emergency treatment should be readily available in case of a severe allergic reaction following the challenge. Important: Never try an oral challenge at home, without medical supervision.

An elimination diet is a short-term eating plan where certain foods are removed and then slowly reintroduced to identify which ones are causing a reaction. Allergists tend to avoid elimination diets for babies. Cutting out foods can sometimes cause new allergies.

Some babies have FPIES, a non-IgE condition which stands for Food Protein-Induced Enterocolitis Syndrome. In FPIES, a baby has severe vomiting, diarrhea and belly pain a few hours after eating. No skin or blood tests can pinpoint FPIES. Instead, doctors monitor what happens when a baby eats food.

When food allergies are hard to figure out

Sometimes, it’s not always clear why your baby is reacting to a particular food. Food allergies are not always IgE-mediated.

IgE-mediated: These are fast allergic reactions that can be very serious and happen right away, like anaphylaxis (serious food allergy).

Non-IgE-mediated: These are slower reactions, mostly in the stomach or intestines, and they might not be life-threatening. Examples include FPIES, proctocolitis, and EOE.

If your baby might have FPIES (Food Protein-Induced Enterocolitis Syndrome), it’s important to tell your healthcare team exactly what you see. Keep track of what foods seem to cause symptoms, when the symptoms start, and how your baby reacts. Common signs include delayed (1-4 hours) repeated vomiting, diarrhea, unusual sleepiness, or appearing very weak. Writing down the time symptoms start after eating and how long they last can help your healthcare team figure out if FPIES could be the cause.

When you talk to your healthcare team, be sure to mention any warning signs that might need urgent care, like severe vomiting, signs of dehydration (fewer wet diapers, dry mouth), or extreme tiredness. They may review your baby’s health history, order tests, or refer you to an allergist or gastroenterologist who knows about FPIES.

Together, you and your healthcare team can make a plan to keep your baby safe. This plan may include avoiding certain foods, knowing when to get medical help, and steps to take if your baby has a reaction. Keeping a simple log of foods and symptoms makes it easier to communicate clearly and helps your healthcare team make the best plan for your baby’s care.

If your baby might have FPIAP, it’s important to tell your healthcare team exactly what you notice. Common signs include blood-streaked or mucus-filled stools, mild diarrhea, or sometimes fussiness after feeding. Keep track of when these symptoms appear, which foods your baby ate, and how often it happens. Writing this down will help your healthcare team understand the pattern and figure out the cause.

Also, be sure to mention any other symptoms or changes in your baby’s health, like poor weight gain or signs of discomfort. Your healthcare team may review your baby’s feeding history, check growth, and examine stool samples. Sometimes, they may refer you to a pediatric allergist or gastroenterologist if the symptoms are persistent or severe.

Together, you and your healthcare team can make a care plan. This may include avoiding certain foods if you are breastfeeding, using special formulas if needed, and monitoring your baby’s symptoms. Keeping a simple log of foods and reactions will make it easier to communicate with your healthcare team and help ensure your baby stays safe and comfortable.

If your baby might have Eosinophilic Esophagitis (EoE), it’s important to share what you notice with your healthcare team. Common signs include trouble swallowing, gagging, vomiting, refusing certain foods, or poor weight gain. Keep track of which foods seem to cause problems, how your baby reacts, and how long the symptoms last. Writing this down can help your healthcare team understand what might be causing the problem.

When you talk to your healthcare team, describe any feeding difficulties, pain, or changes in eating habits. They may review your baby’s feeding history, growth, and medical history. Sometimes, they may refer you to a pediatric gastroenterologist or allergist for further evaluation, which could include tests or an endoscopy to check for inflammation in the esophagus.

Together, you and your healthcare team can make a care plan to help your baby eat safely and grow well. This may include avoiding certain foods, monitoring symptoms, and following up with specialists. Keeping a simple log of foods, reactions, and feeding patterns will make it easier to communicate with your healthcare team and help your baby get the care they need.

Avoiding Common Misdiagnoses

Diagnosing if someone has a food allergy can be tricky. Doctors look at test results and ask about the patient’s health history. They try to tell the difference between allergies and conditions that can look like food allergy symptoms. Doctors pay attention to many clues to make the right diagnosis.

Distinguishing allergies from intolerances

A food intolerance is different from a food allergy. It is not an immune reaction. Instead, it happens when the body can’t break down certain foods. Babies may get tummy pain, gas or diarrhea. The most common type is lactose intolerance, which means the body can’t digest milk sugar.

Food intolerance only affects digestion. It can be uncomfortable, but it is never life-threatening.

A food allergy reaction involves the immune system. Food allergy symptoms include hives, swelling or even a life-threatening reaction called anaphylaxis. Knowing this difference helps parents decide on simple diet changes or when to see an allergist.

False positives in skin/blood tests

A false positive happens when a test suggests your baby has a food allergy, but the baby can eat the food without having a reaction.

Skin prick and blood tests look for IgE antibodies – the “allergy antibodies” that signal the immune system is paying attention to a food. But having IgE doesn’t always mean a true allergy. Many babies eat those foods with no problems at all.

Babies with eczema often make more IgE, which increases the chance of false positives. That’s why test results can be tricky to interpret.

Doctors combine test results with your baby’s history and symptoms to make a diagnosis. Never try to interpret food allergy tests on your own. Always work with a board-certified allergist to decide which foods truly need to be avoided – and which ones can safely stay in your baby’s diet.

Misdiagnosis or overlapping issues

Babies can have other problems that mimic food allergy reactions:

Viral infections. A cold or roseola can give a baby a rash or hives. When the body fights a virus, the skin can get red, itchy spots that look like an allergy.
Mood changes. Babies can get cranky or clingy after eating sweets or foods that upset the stomach.
Celiac disease. This is an autoimmune condition where eating gluten – a protein found in wheat, barley, and rye – causes the body’s immune system to attack the small intestine. Over time, this damages the intestinal lining and makes it harder to absorb nutrients from food.

What to Do After an Allergy Diagnosis

Once your baby has a confirmed food allergy, work with your child’s allergist. Set up clear food allergy prevention plans for home and daycare. You’ll need to learn exactly what to do if your baby has a reaction.

Create a customized allergy action plan

Work with your allergist to create a clear anaphylaxis action plan that you can share with everyone who cares for your baby. The plan should include:

Foods to avoid: A list of your baby’s specific food allergens.
Emergency steps: How to spot a reaction and what to do first.
Medicine use: When and how to give epinephrine or other prescribed medicines.
Emergency contacts: When to call 911 or go to the nearest emergency room.

Make lifestyle changes

A food allergy diagnosis means you will need to develop a broad prevention strategy to help keep your baby safe. You will need to learn how to:

Avoid allergens. This means making daily food choices to help avoid food allergy reactions.
Read food labels carefully for hidden allergens (e.g. “may contain…”).
Prevent cross-contact from allergen exposure on surfaces, cleaning bowls, utensils and high-chairs between foods.
Teach caregivers (family, babysitters, daycare) about how to spot a reaction, what to do, and how to administer epinephrine.
Plan balanced meals with safe foods so your baby gets all the vitamins, nutrients and calories needed to support growth.

Schedule follow-up testing for outgrowing allergies

Some babies outgrow allergies to milk, egg or wheat by age 3–5. Your allergist will:

Repeat testing (skin prick or blood tests) every 6–12 months.
Compare IgE levels over time to see if they go down.
Plan an oral food challenge when tests and history suggest it might be safe to try the food again.
Renew prescriptions (like epinephrine).
Update your action plan as they grow.
Talk about treatment options such as oral immunotherapy or biologic medicines to help your child better tolerate food allergens in case of an accidental exposure.

Questions & Answers (Q&A) on Diagnosing Food Allergies

Diagnosing food allergies in infants requires knowing the signs and symptoms, addressing family history, and conducting tests with a board-certified allergist. Here are answers to some common questions we’re asked about diagnosing infant anaphylaxis.

No. Mail-order kits often measure IgG antibodies, not IgE antibodies. IgG tests only show that the body has had a certain food before. They do not prove an allergy. IgE tests measure what causes true food allergies.

Mail-order tests may give false positives, leading families to cut out certain foods the baby can actually eat safely. Always work with a board-certified allergist, who uses the right tests (skin prick, IgE blood tests, or oral food challenges) and your baby’s history to make a correct diagnosis.

Mail-order results should never replace professional testing and interpretation.

Your child’s allergist will diagnose food allergies using a combination of:

your child’s history of symptoms
a skin prick test or a specific IgE blood test
an oral food challenge conducted under medical supervision
family history of food allergies and other allergic conditions

An oral food challenge is considered the most accurate way to test for a food allergy – it is often called the “gold standard.” In this test, the doctor gives the baby tiny amounts of a food allergen by mouth. Then the doctor slowly increases the amount while watching closely for any reaction.

This direct approach shows exactly how your baby’s body reacts when it eats the food. You see a real reaction or no reaction under safe, controlled conditions.

Tell your doctor exactly what happened when your baby had an apparent reaction. What did your baby eat? When did symptoms start? How did your baby look or feel? Then ask, “Can you send me to an allergist for proper tests?”

To help your doctor, bring:

A food diary showing the food you think caused a reaction and what happened.
A list of symptoms with the time they started and how long they lasted.
Photos of any rash, swelling or other visible reactions.

This clear, simple info should help your doctor see why your baby needs allergy testing. This gets you one step closer to an accurate diagnosis.

A food intolerance is not the same as a food allergy. A food intolerance usually causes tummy troubles like gas, vomiting or stomach cramps. It doesn’t involve the immune system or lead to a severe reaction. The best way to prevent it is to avoid the food that causes the symptoms.