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Common Food Allergies

Soy Allergy

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About Soy Allergy

Soy has become a common ingredient in foods. It’s also a common cause of food allergy. Anyone who has a soy allergy must not eat foods containing soy.

Soy comes from soybeans, which are in the legume family (along with beans, lentils, peas, and peanuts). Some people are allergic to just one type of legume; others are allergic to more than one. Allergy to soy is more common in infants and kids than teens and adults, but can develop at any age.

When someone is allergic to soy, the body’s immune system, which normally fights infections, overreacts to proteins in soy. If the person eats something made with soy, the body thinks these proteins are harmful invaders.

The immune system responds by working very hard to fend off the invader. This causes an allergic reaction, in which chemicals like histamine are released in the body. The release of these chemicals can cause someone to have these symptoms:

  • wheezing
  • trouble breathing
  • coughing
  • hoarseness
  • throat tightness
  • stomachache
  • vomiting
  • diarrhea
  • itchy, watery, or swollen eyes
  • hives
  • red spots
  • swelling
  • a drop in blood pressure, causing lightheadedness or loss of consciousness

Allergic reactions to soy can differ. Sometimes the same person can react differently at different times. Most reactions to soy are mild and involve only one system of the body, like hives on the skin. Other times the reaction can be more severe and involve more than one part of the body.

Anaphylaxis Is a Life-Threatening Reaction

Although rare, soy allergy can cause a severe reaction called anaphylaxis. Anaphylaxis can begin with some of the same symptoms as a less severe reaction, but then can quickly worsen, leading someone to have trouble breathing or to pass out. If it is not treated, anaphylaxis can be life threatening.

Managing Serious Reactions

If your child has been diagnosed with a life-threatening soy allergy (or any kind of life-threatening food allergy), the doctor will want him or her to carry an epinephrine auto-injector in case of an emergency.

An epinephrine auto-injector is a prescription medicine that comes in an easy-to-carry container about the size of a large marker. It’s simple to use. If your child needs to have it on hand, your doctor will show you how to use it.

Kids who are old enough can be taught how to give themselves the injection. If they are responsible for carrying the epinephrine, it should be nearby, not locked in a locker or in the nurse’s office.

Wherever your child is, adult caregivers should always know where the epinephrine is, have easy access to it, and know how to give the shot. Staff at your child’s school should know about the allergy and have an action plan in place. Your child’s rescue medications (such as epinephrine) should be accessible at all times.

If your child starts having serious allergic symptoms, like swelling of the mouth or throat or difficulty breathing, give the epinephrine auto-injector right away. Seconds count during an episode of anaphylaxis. Then call 911 or take your child to the emergency room. Your child needs to be under medical supervision because even if the worst seems to have passed, it’s common for a second wave of serious symptoms to occur.

It’s also a good idea to carry an over-the-counter (OTC) antihistamine for your child, as this can help treat mild allergy symptoms. Use antihistamines after — not as a replacement for — the epinephrine shot during life-threatening reactions.

Living With Soy Allergy

If allergy testing shows that your child has a soy allergy, the doctor will provide guidelines on how to stay safe. Your child will need to completely avoid products made with soy. This can be tough as soy has become part of many processed foods.

Asian foods, infant formulas, and baked goods are just a few of the foods that often contain soy. For more information on foods to avoid, check sites your doctor recommends, such as the Food Allergy and Anaphylaxis Network.

You should always read labels to see if a packaged food contains soy. Manufacturers of foods sold in the United States must state in understandable language whether foods contain any of the top eight most common allergens, including soy. The label should list “soy” in the ingredient list or say “Contains soy” after the list.

This label requirement makes things a little easier. But you still may want to learn the names of some common ingredients that mean soy. It’s also important to remember that “safe” foods could become unsafe if food companies change ingredients, processes, or production locations.


Cross-contamination means that the allergen is not one of the ingredients in a product, but might have contaminated it during production or packaging. Companies are not required to label for cross-contamination risk, though some voluntarily do so. You may see advisory statements such as “May contain soy,” “Processed in a facility that also processes soy,” or “Manufactured on equipment also used for soy.”

Since products without precautionary statements also might be cross-contaminated and the company simply chose not to label for it, it is always best to contact the company to see if the product could contain soy. You might find this information on the company’s website or you can contact a company representative via email.

Eating Away From Home

When your child eats in a restaurant or at a friend’s house, find out how foods are cooked and exactly what’s in them. It can be hard to ask a lot of questions about cooking methods, and to trust the information you get. If you can’t be certain that a food is soy-free, it’s best to bring safe food from home.

Watch for cross-contamination, as soy can get into a food product because it is made or served in a place that uses soy in other foods. This can happen on kitchen surfaces and utensils — everything from knives and cutting boards to a toaster. This is common in Asian restaurants, where soy is often used as an ingredient, and anyplace with communal grills (like hibachi restaurants). Buffets also can be risky since utensils may be moved from one food to another.

Also talk to the staff at school about cross-contamination risks for foods in the cafeteria. It may be best to pack lunches at home so you can control what’s in them.

Here are some other precautions to take:

  • Don’t feed your child cooked foods you didn’t make yourself — or anything else with unknown ingredients.
  • Tell everyone who handles the food — from relatives to restaurant waitstaff — that your child has a soy allergy.
  • Make school lunches and snacks at home where you can control the preparation.
  • Don’t eat at a restaurant if the manager or owner seems uncomfortable about your requests for a safe meal.

Reviewed by: Larissa Hirsch, MD
Date reviewed: September 2012