What Are Soy Intolerance Symptoms in Kids?

What Are Soy Intolerance Symptoms in Kids?

Uncover signs of soy intolerance in kids and learn how to manage it effectively through dietary modifications.

a woman with long blonde hair smiling for the camera
By Emily Hirsch
Dorian Rhode
Edited by Dorian Rhode

Updated April 17, 2024.

A little girl drinking a glass of soy milk.

Table of contents

Show More

If your child has an allergy, you are not alone. According to the American College of Allergy, Asthma, and Immunology, allergies in infants and children are among the leading diagnoses of chronic diseases in childhood.

Results from a 2018 study estimated that 5.6 million children in the U.S., or nearly 8%, have food allergies. That equates to 1 in 13 children or approximately 2 in every classroom.

While any food can cause an allergic reaction, according to the American Academy of Pediatrics, 90% of food allergies in children are caused by just 6 common foods or food groups. These food or food groups include milk, eggs, peanuts, tree nuts, soy, and wheat. In fact, we cover in detail all the soy allergy foods to avoid.

What Is Soy?

Soy foods are made from soybeans. Soybeans are a member of the legume family, and can be found in various forms within a variety of foods.

Soy is a common ingredient in infant formulas and numerous other processed foods. In infants and children, soy is among the top 6 common food allergens.

The legume family includes many different types of beans, and also includes peanuts and lentils.

You may be wondering if your child can eat other legumes if they have an allergy to one legume. The good news is that 95% of people who are allergic to one legume can eat and tolerate other legumes, which decreases the need for further food restrictions.

A baby holding a sippy cup with the text "What is a soy allergy?"

What Is a Soy Allergy?

Allergy to soy is common particularly among infants and young children. A soy allergy is an allergy to the soybean plant, in addition to foods like soybean oil and soy milk that are made from soybeans. 

If your child has a soy allergy, their immune system mistakenly treats soy proteins as harmful invaders. This prompts your child’s immune defenses which can lead to various symptoms that can range from mild to severe. There are two main types of soy allergies: 

IgE-Mediated Soy Allergy 

When your child has an IgE-mediated soy allergy, their immune system makes unique antibodies called IgE antibodies to soy proteins to help fight them. These IgE antibodies generate symptoms of an allergic reaction whenever your child eats a food containing soy. Symptoms of an allergic reaction can occur within seconds to hours after they eat soy. 

Non-IgE-Mediated Soy Allergy

Non-IgE-mediated soy allergies also involve the immune system, but they don’t include IgE antibodies. Non-IgE-mediated soy allergies typically cause gastrointestinal symptoms hours to days after your child eats soy.

There are different types of non-IgE-mediated soy allergies:

  • Food protein-induced enterocolitis syndrome (FPIES) is a rare type of food allergy that typically affects babies. FPIES is commonly triggered by a reaction to milk, soy, oats and rice. FPIES can cause vomiting around 2-4 hours after a child eats soy, and can also cause diarrhea. Severe vomiting and diarrhea can lead to severe dehydration, which may require urgent medical attention.
  • Food protein-induced allergic proctocolitis (FPIAP or allergic proctocolitis) causes inflammation in the lower part of the intestine when a child consumes soy. This allergy is typically caused by cow’s milk or soy and is generally seen in babies under one year of age. FPIAP usually causes abnormal stools that may be bloody, watery, or filled with mucus.
  • Eosinophilic esophagitis (EoE) causes eosinophils, white blood cells linked with allergies, to build up in the esophagus. This causes a child’s esophagus to become inflamed, which creates pain when swallowing. Common food triggers of EoE may include milk, soy, egg, and wheat.  Symptoms of EoE in babies and children can include vomiting, irritability, decreased appetite, chest pain, abdominal pain, reflux-like symptoms, and poor weight gain.

Risk Factors for Developing a Soy Allergy

There are certain factors that may put your child at greater risk of developing a soy allergy.

For example, having a family history of allergies may place your child at increased risk. If other allergies, like hay fever, asthma, hives, or eczema, are common in your family, your child may be at increased risk of developing a soy allergy.

Additionally, having other food allergies may increase your child’s risk of having a soy allergy. Children who are allergic to wheat, beans, milk, or other foods may also have an allergic reaction to soy.

» Gain insight into why you should avoid soy-based formulas

A little boy sitting on a couch with his hands on his stomach.

What Is the Difference Between a Soy Allergy and a Soy Intolerance?

Both a soy allergy and a soy intolerance can lead to similar symptoms. However, the difference between a soy allergy and a soy intolerance lies within the body’s response to the allergen.

A soy allergy reaction involves your child’s immune system. If your child has a soy allergy, their immune system will identify the soy protein as an invader or allergen. Your child’s immune system will then overreact by producing antibodies called Immunoglobulin E (IgE). These antibodies travel to various cells throughout the body that release chemicals, causing an allergic reaction. 

Unlike a soy intolerance, a soy allergy can cause a serious or even life-threatening reaction by eating the slightest amount and touching or inhaling the food. Symptoms of a soy allergy are generally seen on the skin in the form of hives, itchiness, and swelling. A soy allergy can also lead to gastrointestinal symptoms, including vomiting and diarrhea. Your child may also experience respiratory symptoms like wheezing or runny nose as a result of their soy allergy.

Anaphylaxis is a serious life-threatening allergic reaction that may include difficulty breathing, dizziness, or loss of consciousness. Although rare in a soy allergy, anaphylaxis without immediate treatment can be fatal.

Rather than triggering the immune system, a soy intolerance response takes place in your child’s digestive system. Soybean intolerance symptoms may include diarrhea, vomiting, stomach pain, and abnormal stools.

If your child eats a food they are intolerant of, they may experience unpleasant symptoms. However, if your child has a true soy allergy, their body’s reaction to soy could be life-threatening, and it may be best to start early and look for a soy-free formula for your child.

Symptoms of a Soy Allergy

Symptoms of an IgE-mediated soy allergy usually develop seconds to minutes after eating a soy product, and almost always within 2 hours. Soy allergy symptoms in kids or adults can range from mild to severe. IgE-mediated soy allergy symptoms may include:

  • Vomiting, stomach cramps, diarrhea, indigestion
  • Itchy, watery eyes, runny nose
  • Difficulty swallowing
  • Wheezing, shortness of breath, difficulty breathing
  • Repetitive cough
  • Tightness in throat, hoarse voice
  • Weak pulse
  • Pale or blue coloring of the skin
  • Itching, hives (red raised bumps on the skin)
  • Swelling of the face, including the tongue, lips, eyes, or throat
  • Dizziness, fainting, confusion

Signs and Symptoms of Soy Intolerance

Symptoms of a non-IgE-mediated soy allergy usually develop hours to days after eating a soy product. Symptoms of soy intolerance may include:

  • Vomiting
  • Diarrhea, stomach pain, abnormal stools
  • Decreased appetite, poor weight gain
  • Reflux-like symptoms
  • Gas and bloating
  • Irritability, lethargy
  • Hives

Do Children Usually Outgrow Soy Allergies?

Most children will eventually outgrow their soy allergy. One study found that about 25% of children outgrow their soy allergy by age 4, roughly 45% outgrow their soy allergy by age 6, and nearly 70% outgrow it by age 10.

2020 study reported that the highest prevalence of soy allergy (1.5%) was found at age 1 year, however, after age 1, prevalence rates steadily decreased to a low of 0.2% at age 14 to 17 years. This recent research is encouraging news for families concerned about whether their children will outgrow their soy allergy or not.  

The chance of outgrowing soy allergy may depend on whether it is IgE-mediated or non-IgE mediated. Non-IgE mediated soy allergies are usually outgrown in early childhood. IgE-mediated soy allergies can be outgrown, but, in some cases, may persist throughout one’s life.

» Discover top nutrition tips and tricks for all ages

A wooden table topped with soy products like tofu, soy milk, edamame, etc.

What Foods Should a Child with a Soy Allergy Avoid?

Children with soy allergies will have to strictly avoid all soy and products containing soy. Since even the slightest intake of soy could potentially cause an allergic reaction. In order to keep your child safe, it’s imperative that you always carefully read food labels.

Soy is one of the eight major allergens that must be listed on packaged foods sold in the U.S., as required by federal law. Despite this requirement, avoiding soy can still be tricky. Here's what you should avoid.

Soy and soy products to strictly avoid

  • All types of soy milk, soy cheese, soy yogurt, and soy ice cream 
  • Soybean oils, including cold-pressed, extruded, and expelled soybean oil
  • Many children with soy allergies can safely eat highly refined soybean oil. It is best to speak with your allergist to make sure highly refined soybean oil is okay for your child to consume.
  • Soy sauce
  • Soy nuts and soy “nut butter”
  • Soy protein, including concentrated soy protein, hydrolyzed soy protein, isolate soy protein
  • Soy albumin
  • Soy flour
  • Soy fiber
  • Soy grits
  • Soybean curd
  • Soybean granules
  • Soy lecithin
  • Some children with soy allergies can safely eat soy lecithin, but it is important to consult your allergist to make sure soy lecithin is safe for your child to eat.
  • Any other ingredient containing the word “soy” or “soybean”

Foods that may contain hidden soy

  • Bread rolls and other baked goods
  • Candies
  • Cereals
  • Chocolate bars
  • Crackers
  • Chicken nuggets
  • Processed meats
  • Plant-based “alternative meats” (vegetarian or vegan substitutes for meat products, like burgers and chicken, as many are soy-based)
  • Baby formulas
  • Broths
  • Margarine
  • Canned meat and fish
  • Low-fat peanut butter
  • Granola bars/ nutrition bars
  • Sauces
  • Products with “natural flavors” (the “natural” flavoring may include soy)

Foods containing soy under a different name

  • Edamame (another name for soybeans)
  • Miso (fermented soybean paste used as seasoning)
  • Soya, or any product with soya in its name (another way to write “soy”)
  • Shoyu (Japanese-style soy sauce)
  • Tamari (another type of Japanese soy sauce)
  • Teriyaki (sauce)
  • Worcestershire sauce
  • Kinako (soy flour)
  • Nimame (simmered soybeans)
  • Okara (soy pulp)
  • Tempeh (cake-like fermented soybeans)
  • Tofu (blocks of condensed soy milk/soybean curd)
  • Textured vegetable protein (soy-based alternative to ground meat)

Many Asian restaurants can be problematic for children with soy allergies. Many of the foods found in Chinese, Indian, Japanese, Indonesian, Thai, and Vietnamese restaurants contain soy.

Even if you order food that doesn’t contain soy, there is still a high risk of cross-contamination within restaurants.

When shopping, also look out for products that say "may contain soy" or "manufactured on equipment that also processes soy."

This is a sign that there was likely cross-contamination in the plant where the product was produced. Consequently, there could accidentally be traces of soy in these products.

How Can You Tell if Your Child Has a Food Intolerance?

Food intolerances generally take place in your child’s digestive system and can cause unpleasant GI symptoms. While they are uncomfortable, they’re typically not dangerous in the way that food allergies are.

Symptoms of food intolerance can vary by child, the type of food that causes the reaction, and the amount of the food eaten.

If your child has an intolerance to soy and they eat a small amount, they may not experience any symptoms. However, if they eat a large amount of soy, they may experience severe GI discomfort.

The symptoms of food intolerance are often delayed and can appear anywhere from two hours up to two days after your child has eaten the food they’re intolerant of.

Many people may have an intolerance to many different foods, however, the three most common food intolerances are:

  • Lactose- the sugar found in milk
  • Casein- a protein found in milk
  • Gluten-a protein found in grains such as wheat, rye, and barley.

Distinguishing a food intolerance from a food allergy is difficult as many of the symptoms of food intolerance are shared with food allergies and other conditions of the GI system.

Symptoms of food intolerance in children include:

  • Colic or irritability
  • Trouble sleeping, lethargy
  • Gas, bloating, reflux, diarrhea
  • Mucous in the stool
  • Greenish colored stool
  • Eczema
  • Refusing the breast if breastfed

Food intolerances are most commonly diagnosed by following an elimination diet. An elimination diet involves methodically eliminating “suspect” foods from the diet and slowly reintroducing them in an attempt to link symptoms to a specific food or foods.

If your baby is being exclusively breastfed they may be reacting to a food that has passed through the breastmilk. In this case, the breastfeeding mother may need to eliminate the suspect food from their diet.

If you suspect your child has a food intolerance, it’s important to speak with your healthcare provider. A healthcare provider will be able to rule out other serious conditions that may masquerade as a food intolerance. These include celiac disease, inflammatory bowel disease, and gastrointestinal infections.

Testing for Soy Allergies

To make a proper diagnosis, an allergist will ask detailed questions about your child’s allergy symptoms. Keeping a food journal to record information about what your child is eating and which symptoms they are experiencing can be extremely helpful.

An allergist will likely ask questions about what and how much your child ate, how long it took for symptoms to develop, which symptoms they experienced, and how long the symptoms lasted. 

Oftentimes an allergist will pair the answers to these questions with different tests to confirm whether your child has a soy allergy. These tests may include:

Skin prick test

A skin prick test involves placing a drop of the suspected allergen on the skin. A needle is used to prick the top layer of skin so a small amount of the allergen can enter the skin. If your child is allergic to soy, a red bump will appear at the spot of the prick.

Intradermal skin test

In an intradermal skin test, a larger amount of the suspected allergen is injected underneath your child’s skin with a syringe. This test may be more sensitive than a skin prick test. Again, if your child is allergic to soy, a red bump will appear at the spot of the injection. 

Radioallergosorbent test (RAST)

The RAST is a blood test that can measure the amount of the IgE antibody in the blood. This test is sometimes performed on babies under a year old because their skin doesn’t react as well to prick tests.

A baby in a high chair holding a spoon in it's mouth.

How to Test for Soy Allergies at Home

An allergist may recommend that you use an elimination diet with your child at home. The elimination diet seeks to eliminate or isolate suspected foods that can cause a reaction. The following are the steps involved in following an elimination diet:

Step 1. Start a Food Journal

Spend at least one week writing down everything your child eats throughout the day. Note any symptoms your child may experience, the time they happen, and for how long.

Step 2. Note Possible Suspects

Review the food journal keeping in mind that reactions to food can happen anywhere from minutes to days after your child eats a particular food. Write down possible suspects or foods that appear to trigger a reaction.

Step 3. Begin the Food Elimination Process

Remove the foods you’ve identified as possible suspects and make an effort to help your child avoid these foods. Try to eliminate these foods for at least 2 weeks. 

Step 4. Implement the Food Challenge

Once your child is symptom-free, you can begin to implement the food challenge. The food challenge involves reintroducing the suspected foods one at a time and carefully watching for symptoms. If the food challenge results in symptoms, do not continue the challenge until your child is symptom-free for at least 24 hours.

It is important to understand that an elimination diet should only be initiated under the supervision of an experienced healthcare professional. This is to avoid further complications and possible undernourishment.

Prevention of Soy Allergies

While it’s not possible to prevent a food allergy, the American Academy of Allergy Asthma and Immunology recommends the following measures to help reduce the risk of soy allergy.

When possible, exclusively breastfeed your baby for the first four to six months, or use a hypoallergenic formula. Breast milk will help strengthen your baby’s immune system and may reduce the risk of allergies.

Introduce solid foods at around the age of 6 months. Begin by introducing your child to mild foods like apples, pears, bananas, sweet potatoes, squash, carrots, rice, or oats. Try to introduce one food item at a time and continue it for three to five days. This will help you to identify any intolerances or allergies.

After you know your baby can tolerate mild foods, introduce common allergic foods like soy, eggs, milk, peanuts, and fish. New research has shown that delaying the introduction of allergenic foods for a baby’s first 1-3 years of life can actually increase their food allergy risk. Instead, try introducing your baby to common allergenic foods early and often, between 4-11 months of age. 

If your baby has an allergy to any food, then consult your healthcare provider before introducing soy. Discuss with your provider about the quantity of soy that would be safe to introduce.

A young boy holding a red pepper and broccoli.

Healthy Alternatives to Soy

If your child is diagnosed with a soy allergy or a soy intolerance, removing soy from their diet can be complicated. To further complicate things, your child may also have an intolerance to both soy protein and milk protein, a condition known as Milk Soy Protein Intolerance (MSPI).

MSPI is an intolerance to the proteins in milk and soy that a child will eventually outgrow. Both breast-fed and formula-fed babies can develop MSPI. In fact, as many as 2 to 7% of babies in the U.S. under the age of 1 have an intolerance to cow's milk, and over half of those babies may also develop an intolerance to soy proteins.

While removing soy from your child’s diet may be complicated, removing both soy and milk may leave your head spinning. Thankfully, there are many different healthy alternatives to both soy and milk to ensure optimal growth and development in your child.

The popularity of milk alternatives and soy-free products is on the rise.

Milk alternatives may include, coconut, rice, cashew, and almond milk. Hemp milk, oat milk and milk made from pea protein are also available alternatives.

The majority of milk alternatives are fortified with calcium and vitamin D, similar to the amounts found in cow’s milk. However, many milk alternatives are lacking in protein and contain fillers and other additives.

Dairy-free alternatives for children may lack the calories and fat found in milk, in addition to other important nutrients and vitamins.

Try Something Else

In the past, if you were seeking out an allergy-friendly, plant-based, vegan, and ethical option that was nutritionally appropriate for your growing toddler, you would have come up empty-handed. Now there is Else.

Allergy-friendly Else Plant-Based Complete Nutrition is the ideal milk alternative for 1-year-old toddlers and older as it provides the ideal amounts of protein, fat, fiber, vitamins, and minerals to ensure your child’s optimal growth and development.

The content and advice provided in this article are for informational purposes only and are not a substitute for medical diagnosis, treatment, or advice for specific medical conditions. Always consult a pediatrician to understand the individual needs of your child.