Allergen Introduction: A Guide to Safely Introducing Common Allergens to Infants

Introducing foods is a challenging time, but when considering adding in allergens during those early months of introduction, that can be anxiety inducing. But research has shown that introducing the top allergen foods, like peanuts, eggs and dairy sooner than later, may prevent allergies. This appears to be even more true for those at higher risk of allergies, such as those with other family members with allergies or if the baby has eczema. So when should you introduce allergens and how do you do it? 

Why is Allergen Introduction Important?

Early introduction of allergens may prevent allergic reactions to food. And with allergic reactions being scary, and potentially life threatening events, this is definitely something we want to prevent. The Academy of Allergy, Allergy and Immunology defines an allergic reaction as something that "occurs when the immune system overreacts to a harmless substance known as an allergen.” And while an allergic reaction begins in the immune system, it can affect many areas of the body, from the nose to the lungs, sinus, lining of the stomach or the skin. In more serious cases it can cause a life-threatening reaction known as anaphylaxis.

Allergy vs. Intolerance

An allergy, as mentioned above, involves the immune system, whereas an intolerance does not. An intolerance takes place in the digestive system. And since allergies can affect the digestive system, sometimes the symptoms can be similar. A true food allergy affects the immune system, so even a small amount of the allergen can trigger a range of symptoms, that can be severe, whereas, with an intolerance you may be able to eat a small amount of the food without any symptoms.

Common Allergic Reactions

Symptoms of allergic reactions can be seem throughout the body when the immune system reacts to protect you. Symptoms of an allergic reaction can be seen in the following ways:

  • On the skin, with hives, itching, or swelling
  • With gastrointestinal symptoms like vomiting or diarrhea
  • With respiratory symptoms like coughing or wheezing
  • Or with symptoms of anaphylaxis, which include difficulty breathing, dizziness or loss of consciousness

What Are the Top 9 Allergens?

Although it is possible that most any food could cause an allergic reaction, there are 9 foods that cause more than 90% of the reactions.

The Top 9 Allergens


Milk is the most common food allergy in infants, with about 2.5% of children under 3 allergic to cow's milk. Most children eventually outgrow their milk allergy, or may tolerate milk baked into another food product.


Peanuts are the most common allergy in children under 18 (about 2% of children have a peanut allergy), and the third most common allergy in adults. Did you know peanuts are not the same as tree nuts? Peanuts are actually legumes (like beans, peas and lentils) that grow underground, whereas tree nuts grow on trees.


Egg is another common food allergy in infants and young children, but one most grow out of, or will be able to tolerate baked egg. Kids are typically allergic to the protein part of the egg, which is in the whites, but if your child has an egg allergy, they should also avoid the yolks.


Soy is a more common allergy in infants and young children vs. older children, and most will outgrow this allergy. Children with a soy allergy may be more sensitized to peanuts.


Wheat allergy is most common in children, but about two thirds will outgrow their allergy by age 12. A wheat allergy is different than celiac disease. A wheat allergy results from an immune mediated reaction, whereas celiac is an autoimmune disease in which antibodies are produced in the presence of gluten.

Tree Nuts

Tree nut allergies are in common in both adults and children. About 2% of the population has a tree nut allergy, and children with a tree nut allergy will likely carry it into adulthood. The six most commonly reported allergies come from: walnuts, almonds, hazelnuts, pecans, cashews and pistachios. Of children with a tree nut allergy, about 50% have an allergy to another tree nut.


A fish allergy is typically lifelong and many will develop a fish allergy in adulthood. About 1% of the population have a fish allergy.


Shellfish is also typically a lifelong allergy, with 60% of people first developing symptoms in adulthood. About 2% of the population has a shellfish allergy. Shellfish includes both crustaceans (shrimp, lobster, crab) and mollusks (scallops, oysters, clams), with crustaceans responsible for most of the allergies.


Sesame became the 9th major allergen that must be included on food labels in the US last year. About 0.23% of the population is allergic to sesame.

When and How to Introduce Allergens

We want to introduce allergens early, so that means as soon as you start introducing other foods you will want to start introducing the top 9 allergens. There is no reason to delay foods that are thought of as allergens, which was once the practice. There’s a couple extra steps I think you can take when introducing allergens vs. another less allergenic food.

Tips for Introducing Allergens

  • Make sure your little one is well. You don’t want to feed your baby a new allergen when they are sick, as sometimes the symptoms of an allergy can look similar to illness.
  • Give a new allergenic food when you have a couple hour window to observe them. So this means, don’t offer the food in the evening before bed or before sending your child off to daycare.
  • Give a small amount first and observe. Give about ⅛ of a tsp mixed into another food that has already been tolerated. If there is no reaction you can give them a larger amount.
  • Once you have introduced an allergen, keep feeding it. You will want the allergenic food to remain in regular rotation in your baby’s diet, so feed it, at least a couple of times per week.

A couple more things to consider…you don’t want to give cow’s milk on it’s own to your baby. You should wait until a year to introduce cow’s milk, but you can and should introduce other cow’s milk products like yogurt, cottage cheese and cheese.

And where should you start? Peanuts have been the most studied and proven allergen to have benefit when introduced early, so that is often the one recommended to give first, soon after you have started solids. After that you can introduce eggs. The rest can be introduced between 6 and 12 months based on your preferences.

Many of these allergens can be added to purees or pureed themselves. Thin a nut butter with water, then mix into any puree, or spread a thin amount onto a teething cracker. Eggs can be introduced pureed or added into a simple pancake recipe and given as a strip of pancake. Yogurt is a great way to introduce cow’s milk, soy, and some tree nuts. Fish and shellfish can be pureed or mashed or given as a strip of a limited ingredient fish cake.

So, wrapping it all up, introducing allergens to your little one can feel pretty daunting, right? But listen, recent studies are showing that doing this early on might actually help prevent those scary allergic reactions down the road. You should understand the difference between allergies and intolerances, keep an eye out for common allergic symptoms, and know the top 9 allergens, but that shouldn’t keep you from feeding allergens. It's all about starting early and making them a regular part of your baby's diet. If you need more help along the way on solids food journey or with starting solids I have some great resources for you!


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