Soy Allergy: Symptoms, Testing, and Treatment

Soybeans are part of the legume family, which also consists of peas, beans, peanuts, and lentils. Soybeans are widely used as a source of high-quality protein, fiber, potassium and B vitamins. The versatile consistency of soybeans makes them a popular addition to many types of foods: soybeans can be used as a binding agent to protect against moisture loss, as an oil, or even as a flour. And whether in their natural state or processed, soybeans are often used in Chinese, Japanese, Indian, Vietnamese, Indonesian, and Thai cuisine.

Soy is everywhere – which can pose a problem for those with a soy allergy. You may be at a higher risk of a soy allergy if other allergies run in your family, or if you are allergic to wheat, milk, or other legumes (most commonly, peanuts). An estimated 1.9 million Americans are allergic to soy. It is also one of the most common allergens for infants and young children (along with milk allergy, egg allergy, and peanut allergy). 

Soy allergy develops when the immune system has an adverse reaction to soy protein. Once the body comes into contact with soy, a series of IgE antibodies are released in an attempt to fight off the soy protein. These antibodies then initiate an allergic reaction, marked by a wide range of mild to severe symptoms. See below for an overview of common soy allergy reactions, foods to avoid, and how to diagnose – and treat – a soy allergy. 

Symptoms of a Soy Allergy Reaction

An allergic reaction to soy may appear as quickly as within minutes of eating soy. In some cases, an allergic reaction may take hours to show symptoms. While each patient may experience varying symptoms of a soy allergy reaction, the most common include: 

    • Hives or rash
    • Itching
    • Swelling in the lips, tongue, mouth, throat, or around the eyes
    • Nasal congestion
    • Wheezing or shortness of breath
    • Nausea or vomiting
    • Abdominal pain or discomfort
    • Diarrhea
    • Dizziness 

Soy allergy may trigger a severe allergic reaction, which can result in anaphylaxis. Without immediate treatment, anaphylaxis can be a serious, life-threatening event. Anaphylaxis causes the body to go into shock, and can result in symptoms such as:  

    • Pale or bluish tint on the skin 
    • Throat constriction
    • Shortness of breath
    • Difficulty breathing
    • Confusion and/or dizziness
    • Fainting or loss of consciousness
    • Weak, rapid pulse

If you suspect that you or someone you love may be experiencing anaphylaxis, medical care must be sought immediately. Anaphylaxis is a medical emergency, and must be treated with epinephrine. Those who have a severe soy allergy should always have two epinephrine auto-injectors on hand to deliver rapid treatment in case of accidental ingestion. 

Soy Allergy Testing and Diagnosis

Diagnosing soy allergy can be tricky. Symptoms of a soy allergy reaction may appear in a variety of ways and bodily systems, such as on the skin, in the cardiovascular system, the gastrointestinal tract, and even the respiratory tract. In many cases, a soy allergy can be misdiagnosed as a sensitivity or intolerance, which can create a severe health risk. 

Getting an accurate clinical diagnosis can not only help patients properly treat their food allergy, but it can also improve quality of life by relieving stress and ensuring appropriate dietary restrictions. Food allergy testing and diagnosis for soy allergy can include three methods: 


Skin Prick Test

This is a safe and low-risk test in which the skin is lightly pricked with an allergen. Any skin reactions are closely observed and monitored by a clinician. Most reactions appear as bumps or hives, with mild itchiness as the most common side effect. 

Blood Test

A blood test will measure the amounts of specific IgE antibodies that the immune system has deployed as a response to soy protein. Once drawn, the blood is sent to a lab to be evaluated. Blood tests are safe for infants and children, as well as adults. While the results of a skin prick test are immediate, the results from a blood test often take a few days. 

Oral Food Challenge

This test is particularly useful as the final step in determining whether a food allergy has been outgrown, or when skin and blood tests are inconclusive. An oral food challenge can determine, with certainty, whether soy may safely be consumed. Under close supervision and observation in the clinic, the patient will consume very small amounts of soy in increasing amounts over a three- to four-hour time period. 

This step is only taken after a full review of patient history and only in cases where a clinician determines that a patient is likely to successfully and safely pass the food challenge.

Ingredients to Avoid for Soy Allergy

Soy and soy by-products can be found in many ingredients – particularly in vegan or vegetarian meat alternatives – and may include complex ingredients that don’t always have the word “soy” in them. If you have a soy allergy, watch out for the following ingredients, as they may not be safe to consume.

    • Glycine max
    • Hydrolyzed vegetable protein (HVP)
    • Mono-diglyceride
    • Monosodium glutamate (MSG)
    • Vegetable gum
    • Vegetable starch
    • Textured soy protein
    • Textured vegetable protein
    • Soya
    • Cold-pressed soy oil
    • Expelled soy oil

Studies have demonstrated that many patients with a soy allergy can safely consume soy lecithin. If you have questions about whether this (or any soy-based) ingredient is a safe addition to your diet, talk to your allergist before consuming products with soy lecithin.

Foods That Commonly Contain Soy

Two blocks of white tofu isolated on white.

The Food Allergen Labeling and Consumer Protection Act of 2004 requires all food manufacturers to clearly state whether a food allergen is present. Soy is one of eight allergens that currently fall into this category, which includes any soy-based ingredient. Those with a soy allergy may experience an allergic reaction after eating the following foods:

    • Bean curd
    • Edamame
    • Miso
    • Natto
    • Soy sauce
    • Shoyu sauce
    • Supro
    • Tamari
    • Tempeh
    • Teriyaki sauce
    • Tofu
    • Yuba

Any soy-based foods will fall under this list as well, such as soy cheese, flour, nuts, soy milk, soy yogurt, soy ice cream, or sprouts. Soy may also show up in unexpected foods, such as grains, desserts, and frozen entrees. Patients who have been diagnosed with a soy allergy must pay close attention to ingredient labels for the following:

    • Breads
    • Broth
    • Cookies
    • Crackers
    • Cereals
    • Ice cream
    • Energy bars 
    • High-protein snacks
    • Canned tuna
    • Canned meat
    • Canned soup
    • Low-fat peanut butter
    • Deli meats
    • Meat substitutes 
    • Vegetable oil
    • Worcestershire sauce
    • Salad dressings
    • Gravy
    • Mayonnaise
    • Sauces
    • Infant formula and baby foods

Soy Allergy Treatment Options

Soy allergy can be successfully treated with oral immunotherapy (OIT). This is a safe and effective treatment for children and adults that gradually reduces allergic reactions to food allergens over time. This provides protection against accidental exposure while reducing stress, improving quality of life, and enabling patients to eat a full, balanced diet. 

OIT exposes the patient to incremental doses of allergens, slowly increasing the amount of allergen as treatment progresses. This approach desensitizes and retrains the immune system, decreasing the severity of allergic reaction symptoms. 

OIT is approximately 85% effective when supervised by an expert care team who specialize in food allergy treatment. At Latitude Food Allergy Care, we are proud that 92% of our OIT patients successfully achieve maintenance, and oral immunotherapy is offered with or without Xolair: an anti-IgE monoclonal antibody that helps suppress allergic reactions for some patients.

Are you or someone you love impacted by a soy allergy? Take the next step toward better health and better quality of life with Latitude Food Allergy Care. Our Patient Care Coordinators are happy to discuss your testing and treatment options to determine whether you are a candidate for treatment. Contact us today to schedule your no-obligation call.

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