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Overview

A member of the legume family, soy is a common ingredient in infant formulas and many other processed foods. In young children, soy is one of the most common food allergens. Typically, allergic reactions first appear in infants and young children under 3, and many outgrow the allergy by during childhood.

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Common Triggers of a Soy Allergy

  • Soy and soy products (including some infant formulas), soy milk and soy sauce

Soy Allergy Management

  • Avoid products containing soy. This includes reading labels carefully.
  • Always be prepared to treat an allergic reaction because reactions are unpredictable in severity and can occur anywhere. Epinephrine autoinjectors should be readily available to treat severe allergic reactions or anaphylaxis.
  • Get more information on soy allergy management.

Symptoms

Symptoms of a soy allergy include:

  • Vomiting
  • Stomach cramps
  • Indigestion
  • Diarrhea
  • Wheezing
  • Shortness of breath, difficulty breathing
  • Repetitive cough
  • Tightness in throat, hoarse voice
  • Weak pulse
  • Pale or blue coloring of the skin
  • Hives
  • Swelling, can affect the tongue and/or lips
  • Dizziness
  • Confusion

Rarely, a soy allergy will cause anaphylaxis, a potentially life-threatening reaction that impairs breathing, causes a sudden drop in blood pressure and can send the body into shock. The only medication that can treat anaphylaxis is epinephrine (adrenaline), administered through an auto-injector as soon as symptoms are apparent.

If you or your child experiences any of these symptoms after eating soybeans or a product containing soy, see an allergist.

Diagnosis

Diagnosing soy allergies can be as complicated as the medical condition itself. Symptoms can vary from person to person, and a single individual may not always experience the same symptoms during every reaction.

Allergic reactions to soy can affect the skin, respiratory tract, gastrointestinal tract and/or cardiovascular system.

When a food allergy is suspected, it’s important to consult an allergist, who can determine which tests to perform, decide if an allergy exists and counsel patients on managing exposure and symptoms once the diagnosis has been confirmed.

To make a diagnosis, allergists ask detailed questions about the history of allergy symptoms. Be prepared to answer questions about what and how much you ate, how long it took for symptoms to develop, which symptoms you experienced and how long the symptoms lasted. The allergist will usually perform skin-prick tests and/or order a blood test (such as an ImmunoCAP test), which indicate whether food-specific immunoglobulin E (IgE) antibodies are present in your body.

Skin-prick tests are conducted in a doctor’s office and provide results within 15 to 30 minutes. A drop of a liquid containing the suspected allergen is placed on the patient’s forearm or back. The skin is then pricked with a small, sterile probe, allowing the liquid to seep under the skin. The tests, which are not painful but can be uncomfortable, are considered positive if a wheal (resembling a bump from a mosquito bite) develops at the site.

Blood tests, another testing option for food allergy, measure the amount of IgE antibody to the specific food(s) being tested. Results are typically available in about one to two weeks and are reported as a numerical value.

Your allergist will interpret these results and use them to aid in a diagnosis. While both of these diagnostic tools can signal a food allergy, neither is conclusive. A positive test result to a specific food does not always indicate that a patient will react to that food when it’s eaten. A negative test is more helpful to rule out a food allergy. Neither test, by size of the skin test wheal or the level of IgE antibodies, necessarily predicts the severity of an allergic reaction to soy.

An allergist may use these tests and the patient’s history to make a food allergy diagnosis. For a definitive diagnosis, the allergist may wish to conduct an oral food challenge, in which the patient is fed gradually increasing amounts of the suspected allergy-causing food under strict supervision. Experienced personnel, emergency medication and emergency equipment must be on hand during this procedure.

Oral food challenges also may be performed to determine if a patient has outgrown a food allergy.

Management and Treatment

As with other food allergies, the best way to manage a soy allergy is to avoid consuming products that contain soy.

Soy is one of the eight allergens that fall under the labeling requirements of the Food Allergen Labeling and Consumer Protection Act of 2004. This means that manufacturers of packaged food items sold in the United States and containing soy or a soy-based ingredient must state, in clear language, the presence of soy in the product.

Soy or derivatives of soy are found in some infant formulas, canned broths, soups, canned tuna, processed meats and hot dogs, energy bars, baked goods and many other processed foods. Soy also is a common ingredient in Asian cuisine and is sometimes contained in chicken nuggets, low-fat peanut butter, alternative nut butters and even vodka. People with a soy allergy should not consume soy milk, soy yogurt or ice cream, edamame, miso, tempeh and tofu.

Most individuals allergic to soy can safely consume highly refined soybean oil. Ask your allergist about avoiding this ingredient. Also, be cautious when eating foods that have been fried in any type of oil, due to the risk of cross-contact: If a soy-containing food is fried in oil, that oil will absorb certain soy proteins; if a different food that doesn’t contain soy is then fried in that same oil, consuming it could trigger an allergic reaction.

People with a soy allergy often can eat foods that contain soy lecithin — a mixture of fatty substances derived from soybean processing. If you have a soy allergy, ask your allergist if soy lecithin is safe for you.

People with a soy allergy sometimes wonder if they should also avoid peanuts — another legume that is a common allergy trigger. The answer is “not necessarily.” They are separate foods and their allergen triggers are unrelated. Soybeans also are unrelated to tree nuts such as almonds, walnuts and cashews. Those allergic to soy are no more likely to be allergic to tree nuts or peanuts than they would be to another food.

Talk to an allergist to take control of your soy allergy and live the life you want.

Managing a severe food reaction with epinephrine

Soy is among the most common food allergens. But all food allergies can be dangerous.

Epinephrine is the first-line treatment for anaphylaxis, a severe whole-body allergic reaction that causes symptoms, including tightening of the airway. Anaphylaxis can occur within seconds or minutes of exposure to the allergen, can worsen quickly, and can be deadly.

Once a food allergy diagnosis is made, your allergist likely will prescribe an epinephrine auto-injector and teach you how to use it. Check the expiration date of your auto-injector, note the expiration date on your calendar and ask your pharmacy about reminder services for prescription renewals.

Be sure to have two doses available, as the severe reaction may recur. Epinephrine should be used immediately if you experience severe symptoms such as shortness of breath, repetitive coughing, weak pulse, generalized hives, tightness in the throat, trouble breathing or swallowing, or a combination of symptoms from different body areas such as hives, rashes or swelling on the skin coupled with vomiting, diarrhea or abdominal pain. Repeated doses of epinephrine may be necessary.

If you are uncertain whether a reaction warrants epinephrine, use it right away, because the benefits of epinephrine far outweigh the risk that a dose may not have been necessary.

Common side effects of epinephrine may include transient anxiety, restlessness, dizziness and shakiness. Rarely, the medication can lead to an abnormal heart rate or rhythm, a heart attack, a sharp increase in blood pressure and fluid buildup in the lungs, but these adverse effects are generally caused by errors in dosing which is unlikely to occur with use of epinephrine autoinjectors. Patients with certain pre-existing conditions who may be at higher risk for adverse effects should speak to their allergist about epinephrine use.

Your allergist will provide you with a written emergency treatment plan that outlines which medications should be administered and when (note that between 10 and 20 percent of life-threatening severe allergic reactions have no skin symptoms). Be sure you understand how to properly and promptly use an epinephrine auto-injector.

Once epinephrine has been administered, immediately call 911 and inform the dispatcher that epinephrine was given and that more may be needed from the emergency responders.

Other medications, such as antihistamine and corticosteroids, may be prescribed to treat mild symptoms of a food allergy, but it is important to note that there is no substitute for epinephrine — this is the only medication that can reverse the life-threatening symptoms of anaphylaxis.

Managing soy allergies in children

Because soy allergy reactions, like other food allergy symptoms, can develop when a child is not with his or her parents, parents need to make sure that their child’s school, day care or other program has a written emergency action plan with instructions on preventing, recognizing and managing these episodes in class and during activities such as sporting events and field trips. A nonprofit group, Food Allergy Research & Education, has a list of resources for schools, parents and students in managing food allergies.

If your child has been prescribed an auto-injector, be sure that you and those responsible for supervising your child understand how to use it.

 

This page was reviewed and updated as of 4/9/2019.