Overview of Soy Allergy

Food allergies are common in adults and kids. Approximately 8% of children and 10% of adults in the United States are allergic to at least one food.

This article will give an overview of soy allergies. You will learn what happens if someone is allergic to soy, as well as whether it's possible to outgrow the allergy or develop allergies to other foods.

Soybean food and drink products
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What Is Soy?

Soybeans are a member of the legume family, which includes peanuts, beans, and peas. Soy protein is found in many foods and non-food products.

Soybeans are commonly used in the commercial processing of food because they are a widely available, low-cost, and high-quality protein.

Since soy is so common, children are usually exposed to it while they are still babies.

In fact, soy is used as a substitute for milk protein in some infant formulas. It's said to be a "gentler" formula ingredient, which can be helpful for babies with sensitive digestive systems.

Adults also regularly consume soy as a dietary alternative, particularly if they have a dairy allergy, lactose intolerance, or another form of milk intolerance.

Soy is very popular in some cultures, especially Asian cuisine. You'll find the ingredient in soy sauce, miso soup, and tofu.

Soy Allergy Reactions

Soy allergies can occur in babies, children, and adults. A person with a soy allergy may have different symptoms, including:

Risk of Severe Reactions

A soy allergy can also cause serious, life-threatening reactions, including anaphylaxis.

However, severe reactions do not happen as often with soy allergies as they do with other food allergies, like peanuts and shellfish.

Diagnosis

A soy allergy is typically diagnosed by allergy skin testing. However, blood testing for allergic antibodies against soy protein can also be used.

Non-Allergic Reactions

Soy protein can also cause non-allergic protein intolerance in kids. This condition is called food protein-induced enterocolitis syndrome (FPIES).

Babies and children with FPIES can have nausea, vomiting, diarrhea, dehydration, weight loss, and even develop a serious condition called shock.

Children with FPIES have negative allergy testing to soy because there is no allergic antibody involved.

Around 50% of children with soy-induced FPIES will have a similar reaction to cow’s milk.

A milder form of FPIES caused by soy formula is a condition called food protein-induced proctitis. It causes bloody stools in infants.

Outgrowing a Soy Allergy

Children often outgrow a soy allergy by the time they are 10 years old. Many children actually outgrow the allergy by the age of 3.

Do not try to test if your child is still allergic to soy or any other food. Determining if a child has outgrown an allergy should only be done under medical supervision.

Your child's provider can also do tests to find out how many allergic antibodies your child has against soy, as this information might indicate if they have outgrown the allergy.

Risk of Other Food Allergies

Soy does have similar proteins to those found in other legumes, such as peanuts, peas, beans, and lentils. However, most people with a soy allergy can eat other legumes without having a reaction.

Still, people with a soy allergy are often told to avoid all legumes. That's because allergy tests often show positive allergy results to more than one legume.

These results happen because the proteins similar to the ones found in legumes bind to the same allergic antibodies against soy proteins. This is called cross-sensitization.

Research has shown that when soy-allergic people eat other legumes, true allergic reactions do not happen often. About 95% of people with a soy allergy can eat other legumes.

Can I Eat Other Legumes?

If you are told that you have positive allergy tests to more than one legume, ask your provider before eating these foods.

Managing a Soy Allergy

If you or your child is allergic to soy, it's important to learn how to live with the allergy. There are a few key things you'll need to know to manage it safely:

  • Which foods are safe and which you'll need to avoid
  • What to do in the event of an exposure
  • When to call your provider/seek emergency care

For Severe Allergies

Severe allergies to soy are not common, but they can happen. People with a serious allergy may need to wear a medical alert bracelet or carry an information card with them at all times.

When a person has a severe allergic reaction, they may not be able to ask for help. In these cases, having a card or bracelet that explains they have an allergy can provide life-saving information to first responders.

If you're caring for a child with a severe allergy, make sure that their daycare, school, and other caregivers (like a babysitter) have this information and know what to do.

Summary

Soy is a common ingredient in many foods, as well as non-food products. If you're allergic to soy, it can be hard to avoid.

The good news is, soy allergies usually are not as serious as other food allergies. Babies and young children often outgrow the allergy.

People with a soy allergy should also be tested for other food allergies. Not everyone who is allergic to soy will be allergic to another food. However, some people who are allergic to soy are also allergic to other legumes, like peanuts and beans.

If you or your child has a soy allergy, part of living with the condition is figuring out which products to avoid, making a plan for what to do if an exposure happens, and knowing when to seek medical care.

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11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Children's Hospital of Philadelphia. Soy allergy.

  • University of California San Francisco Health. Soy allergy.