Big 8 Food Allergies [Dietitian FAQ]

The Big 8 food allergies – milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish – account for the vast majority of food allergies in kids. For parents, navigating food allergies can feel overwhelming and confusing, especially when symptoms aren’t always clear or immediate.

In this blog post, I’ll walk you through the most common questions I hear from parents: how to tell the difference between a food allergy and a sensitivity, what signs and symptoms to look for, how allergies are diagnosed, and the latest research about introducing allergens early. 

Whether your child has a confirmed allergy or you’re just trying to stay informed, hopefully this guide will help you feel more confident and prepared!

What are food allergies? How are they different from food intolerances or sensitivities?

Food allergies are defined as a reproducible “adverse health effect” when the immune system reacts to a certain food (3). The key word here is reproducible – the reaction has to occur with every instance of interacting with a certain food. However, some allergies are serving size-dependent or exercise-induced, which makes it challenging to identify allergies.

Food intolerances are different. They don’t involve the immune system and usually cause stomach issues like gas or bloating.

Food sensitivities do not have a clear definition and include any symptom perceived to be related to food ingestion.

The main difference between these terms is that allergies involve the immune system while intolerances and sensitivities affect digestion. This also changes how each one is diagnosed.

What foods are considered “allergen foods”?

The Big 8 food allergies are responsible for about 90% of all food allergies in kids (3). These are the most common culprits when children have allergic reactions to food.

In order of frequency, the Big 8 food allergies include:

1. Milk

2. Eggs

3. Peanuts

4. Tree Nuts

5. Soy

6. Wheat

7. Fish

8. Shellfish

For children under age 3, the most common food allergies are milk, eggs, peanuts, soy, and wheat.

What symptoms should I look for to spot a food allergy?

There are several categories of reactions kids can have to allergies. These occur immediately after food ingestion or several hours after ingestion (3).

Gastro-intestinal Symptoms

• Vomiting
• Abdominal pain
• Diarrhea
• Swelling Tongue
• Itchy Mouth
• Swelling of the lips or tongue

Dermatologic Symptoms

• Skin flushing
• Itchy skin
• Red skin rash
• Welts on the skin or raised hives

Respiratory Symptoms

• Anaphylaxis
• Dry Cough
• Sneezing
• Hoarse Throat

Cardiovascular Symptoms

• Dizziness
• Fainting

How are food allergies diagnosed? 

There are a few ways doctors can help figure out if your child has a food allergy:

1. Food and Symptom History

Your doctor will ask questions about what your child ate and what symptoms followed. This helps narrow down possible allergens.

2. Skin Prick Test (SPT)

Small amounts of potential allergens are placed on the skin. Then, the skin is lightly pricked to see if there’s a reaction.

• A negative result is usually accurate — over 95% of the time, it means no allergy.
• A positive result isn’t always accurate. It can suggest a risk, but not confirm an allergy on its own.

3. Oral Food Challenge

This is considered the most reliable test. It’s done in a clinic or hospital where your child eats a small amount of the food while being closely watched.

Food sensitivities are often tested using blood tests, but these aren’t very reliable. Elimination diets are usually better for spotting sensitivities.

When should I introduce allergen foods?

Allergens should be introduced when your baby starts solids, usually around 6 months. The goal is to offer these foods early and regularly to build tolerance through repeated exposure.

If your child has eczema or another known food allergy, make sure to ask your kid’s pediatrician about introducing the big 8 food allergies, because they are at higher risk for being allergic to foods (4),

In terms of how allergens should be introduced, I’m leaving it to the feeding specialists! Linking a great guide here for introducing allergens within the first 100 days of starting solids. This guides you through gradually increasing the serving size of allergen foods and how to do this one at a time. Check it out!

Does the early introduction of allergen foods help prevent allergies?

Yes! Early introduction (around 6 months of age) to allergen foods reduces the risk of developing an allergy.

There’s strong food allergy research around this for specific foods (5):

• Introducing peanuts at 6 months old can decrease the likelihood of an allergy by 80%
• Introducing eggs within the first year of life leads to a 30% decrease in known allergy
• Introduction to cow’s milk within the first three months of life significantly decreases chances of an allergy within 3-5-year-olds

The thought behind early exposure is “training” the immune system to recognize allergens while it’s still developing. If allergen foods are not introduced, there is a higher chance the immune system will detect it as “foreign”.

Can kids outgrow their allergies?

Yes! But it depends on the food.

Many kids outgrow allergies to milk, eggs, wheat, and soy. This often happens by age 6, though some kids may take longer.

On the other hand, allergies to peanuts, tree nuts, and shellfish are less likely to be outgrown. These usually last into the teen years or adulthood.

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Food allergies can be stressful, but you’re not alone. Understanding the Big 8 food allergies and knowing what signs to look for is a great first step.

If you ever suspect an allergy, bring it up with your child’s doctor. The right diagnosis and a clear plan can make a huge difference.

And remember — early exposure, when done safely, can help reduce the risk. If you need help navigating food allergies or starting solids, reach out to a pediatric dietitian for support.

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