September 2022  |  Linda Armstrong  |  ✓  Medically reviewed by: Fabio Iachetti, MD; Eva Södergren, PhD, MSc

When it’s time to transition infants to solid foods, most parents and caregivers have a plan—or at least another parent, social media, or good ol’ Google to get them through. But often those sources are less helpful when it comes to introducing babies to allergenic foods such as eggs, peanuts, milk, and more. In fact, caregivers are likely left with more questions than answers.

Is there a right—or wrong—time to introduce food allergens to children? Does introducing allergenic foods actually prevent allergies? Or is it better to avoid these allergens until children are older?

And if you do forge ahead, what’s the process? What food allergy symptoms should you watch for? How do breastfeeding and infant formulas impact this process?

If this is your first foray into food-allergen introduction, your head is probably swimming with questions. But don’t worry, the following info offers a deep dive into why, how, and when to introduce babies to food allergens and provides a boatload of tips to maintain the child’s safety—and your sanity.

What are some of the most common food allergies?

Before we examine the “how” and “when” of food-allergen introduction, let’s quickly identify the most common culprits for children (and adults alike). While top allergens vary by location, data from the United States and the European Union identify some worldwide offenders.

The United States Food and Drug Administration (FDA) indicates that the following account for 90 percent of allergic reactions to food in the United States.¹ (Note that sesame has been added to the list starting in January 2023.) 

• Eggs
• Milk
• Fish
• Shellfish
• Tree nuts
• Peanuts
• Wheat
• Sesame
• Soybeans (soya)

Meanwhile, the European Union identifies 14 major allergens for food-ingredient labeling, which include all FDA-recognized allergens above plus those below.² E.U. data breaks down shellfish into crustaceans and mollusks and broadens the wheat category to cereals containing gluten (e.g., wheat, rye, barley, and oats).

• Celery
• Lupin
• Mustard
• Sulphites (aka sulphur dioxide) (used in dried fruits, meat products, soft drinks, etc.)

When should you introduce babies to food allergens?

Surprisingly, the answer to this question has changed within the last decade. Up until roughly 2015, experts recommended that infants avoid allergens such as peanuts until around age 3. The core idea, which was based on expert opinion since clinical studies were lacking, was that limited exposure would prevent the development of allergies.³

These recommendations existed for decades until studies such as Learning Early About Peanut (LEAP) revealed new findings.⁴ In a nutshell, LEAP and other studies suggest that early introduction of allergenic foods actually helps prevent the development of food allergies.⁵ In fact, when it comes to peanut allergy, introducing peanuts to infants with severe eczema and/or egg allergy before they are 12 months of age can reduce their risk of developing peanut allergy by roughly 80 percent.⁶

Revised food-introduction guidelines now indicate that with few exceptions, allergenic foods may be introduced to children between the ages of four and six months of age. Thereafter, regular exposure to food allergens is important for maintaining tolerance.⁵

How do you introduce children to food allergens?

Once the child is four to six months of age, how do you actually introduce children to allergenic foods? Experts offer six key takeaways.

According to the American Academy of Allergy, Asthma, and Immunology (AAAAI), these foods typically include fruits (apples, pears, and bananas), vegetables (sweet potatoes, squash, and carrots), and cereal grains (rice or oat cereal). Restrict food introduction to one new food every three to five days based on the infant’s developmental readiness to eat solid foods.⁷

After less-allergenic foods have been tolerated, the AAAAI recommends adding in eggs, dairy, peanuts, tree nuts, fish, and shellfish. Again, introduce one food at a time over three to five days so you can easily identify any foods that cause reactions.⁷

To help identify the causes of any potential reactions, offer allergenic foods individually rather than within a recipe or purchased product. For example, introduce small pieces of cooked egg instead of egg within a baked product full of other ingredients. You can, however, intro allergenic food along with fruits and vegetables that your baby has already tolerated.⁸

The Australian Society of Clinical Immunology and Allergy (ASCIA) reminds us that all baby foods should be the right size and texture for the child’s stage of development. For example, instead of whole nuts and nut pieces, opt for smooth nut spreads or nut flours to help prevent choking.⁹

If the child doesn’t have any reactions to an allergenic food, continue to include it in his or her regular diet at least three times a week. While experts haven’t identified a firm deadline to stop this introduction schedule, it’s important to keep food allergens as part of a healthy, well-balanced diet to help maintain the child’s allergen tolerance levels.⁸

It’s critical to monitor the baby for food-allergy symptoms after consumption. Thus, the ASCIA recommends you perform initial food introductions when you can most easily monitor the baby and respond if necessary. An ideal time is shortly after the child wakes up in the morning, and try to do so at home rather than at a day care or restaurant.⁹

Are there any exceptions to these food-allergen guidelines?

According to an article in the journal for Allergy, Asthma & Clinical Immunology (AACI) peanuts, food-allergy reactions, and severe dermatitis/eczema present a few caveats.

• Peanut allergies in siblings. Infants with an older sibling with a peanut allergy have an almost sevenfold risk of also having a peanut allergy. The AACI article recommends that a healthcare provider evaluate these infants prior to peanut introduction but suggests that analysis should be performed promptly so you don’t miss the important four-to-six-month food-introduction window.⁵
• Food allergy reactions. Babies that have an allergic reaction to a food should be assessed by a healthcare provider before the same food is introduced again.⁵
• Severe eczema/dermatitis. Healthcare providers should also assess children with moderate to severe dermatitis/eczema before introducing allergenic foods.⁵

What symptoms should you watch for when introducing food allergens to children? 

Allergic reactions typically occur within minutes to two hours of consumption.⁹ So as soon as the baby ingests the allergen, be on the lookout for mild symptoms, which may include:¹⁰

• hives
• swelling of the lips, face, and/or eyelids
• red rash around the mouth
• tingling in the mouth
• stomach pains
• vomiting 

If any of these symptoms occur, stop feeding that food and seek medical advice.⁹

Also look for a more serious food-allergy reaction such as anaphylaxis, which is a rare but life-threatening emergency. Anaphylaxis symptoms include:¹⁰

• difficulty breathing
• swelling of the tongue
• tightness in the throat
• hoarse voice
• cough or wheeze
• collapse

Immediately call an ambulance if the baby shows signs of anaphylaxis.

Is there anything breastfeeding and expectant moms can do to prevent allergies? 

When it comes to the mother, a healthy diet during pregnancy can positively impact the baby’s health. Additionally, breast milk provides excellent nourishment, strengthens the immune system, and is easy to digest and unlikely to trigger an allergic reaction. And while more research is needed, some experts suggest that breastfeeding may reduce early eczema, wheezing, and cow’s milk allergy.⁷

That said, avoiding allergens during pregnancy or while breastfeeding likely doesn’t reduce the risk for allergies in babies.⁵

When it comes to baby formula, there’s conflicting evidence regarding hydrolyzed formulas (which contain milk protein that has been broken down into smaller pieces, making it easier for babies to digest).

Some sources, such as an article in the Journal of Allergy and Clinical Immunology, indicate that hydrolyzed formulas may help prevent cow’s milk allergy.¹¹ However, other studies including an article in the same JACI publication, suggest it’s not recommended for the prevention of allergic disease.¹² Bottom line: Talk to your pediatrician to weigh formula options if needed.

When should you test for food allergies?

Sources such as the Canadian Paediatric Society discourage routine allergy testing prior to food introduction because positive results may be falsely interpreted as an allergy. Such a conclusion could lead to an unnecessary delay in allergenic food introduction—and might cause you to miss the important four-to-six-month window.³

The only exception may be infants at high risk of peanut allergy, i.e., those with severe eczema and/or egg allergy. In this case early tests such as a specific IgE blood test for peanut may be recommended.³ Again, talk with your pediatrician to determine the best course of action.

If you’ve missed the four-to-six-month introduction window or the child is older and having allergy symptoms, blood testing for allergy triggers may be an important tool in your arsenal. After all, in order to help the child avoid his or her allergic triggers, you need to first understand what they are. Particularly given the fact that allergy severity can unexpectedly ramp up from mild symptoms to life-threatening allergic reactions such as anaphylaxis, understanding triggers is paramount.

A simple test called a specific IgE blood test along with a symptom history and physical exam may help your healthcare provider diagnose the child’s allergies.