The Soy Allergy Diet Guide

Soy is prevalent in the American diet. artparadigm/getty images

Soy allergy –-a common food allergy in children, but not so much in adults—occurs in about 0.4% of all children. Odds are that 85% of children with soy allergy will see it resolve by age 5, but half of all children will still have a soy allergy at age 7. By the teen years, most kids will have outgrown it.

Symptoms of Soy Allergy

Symptoms associated with a soy allergy may occur after drinking soy milk or eating soy foods or foods made with soy.

Symptoms may include:

  • Skin reactions such as rash, hives or eczema.
  • Gastrointestinal symptoms like nausea, stomach pain, vomiting, or diarrhea.
  • Airway symptoms including wheezing, coughing, or a runny nose.
  • Swelling, also known as angioedema, of the lips, tongue, or face.
  • Severe reactions, called anaphylaxis, may occur, affecting multiple organ systems. However, anaphylaxis to soy is extremely rare.

Soy protein may cause a digestive disorder in childhood called food-protein-induced enterocolitis syndrome (FPIES). This syndrome is characterized by the onset of vomiting and diarrhea several hours after soy has been eaten. In extreme cases, dehydration and failure to thrive (lack of weight gain and overall growth) may occur. Infants can get a similar set of symptoms from cow’s milk protein, known as cow’s milk protein-induced enterocolitis. About 50% of infants who react to cow’s milk with this syndrome will also react to soy.


Some people with peanut allergies may also be allergic to soy protein. People with soy allergies may cross-react with peanuts or other legumes, such as beans or peas. However, most people with soy allergy can safely tolerate other legumes because the legume family has over 30 species.

If you suspect an allergy to another legume, you should investigate this legume separately to determine if you have sensitivity. Don’t assume you are allergic to the broad category of beans and legumes just because you have a soy or peanut allergy—you will unnecessarily restrict your diet, which could cause nutritional deficiencies down the road.

Diagnosis of Soy Allergy

Soy allergy is usually diagnosed by a medical doctor (allergist) after a medical history, physical examination, and food allergy testing are performed.

Treatment for Soy Allergy

The treatment for soy allergy is the elimination of soy from the diet.

How to Avoid Soy

As mentioned, all soy must be eliminated from the diet to avoid an allergic reaction. Equally important is to avoid all foods made with soy, like some granola bars, cookies, crackers, and cereals. Soy is found in many food products and is often added to bump up the protein content.

The Food Allergy Labeling and Consumer Protection Act (FALCPA) insists manufacturers list soy as a potential allergen ingredient for the consumer. Not only will you find this information in the ingredients list, but it will also be on the package. Some products won’t call out soy-based ingredients on the label.

There are two things you can do in this situation: call the manufacturer and inquire about the specific ingredients contained in the product, and/or skip eating the product.

Avoid food items that contain these words in the ingredients list, as they indicate the presence of soy: edamame, miso, natto, shoyu sauce, soy fiber, soy flour, soy protein, soy sauce, tamari, tempeh and more. Hidden soy can be a surprise, so avoid accidentally consuming it by reading the ingredients label on the product.

Foods regulated by the USDA or foods purchased abroad may not include the word soy on their label.

Highly refined soybean oil has little protein content and is unlikely to cause a reaction (although if you are very sensitive to soy, speak with your allergist before ingesting products made with soy oil).

Soy lecithin contains a tiny amount of soy protein, unlikely to be enough to cause a reaction. When included in food products, soy lecithin is typically present in small amounts, making the risk for reaction small. FALCPA exempts refined soybean oil and soy lecithin from labeling, however, soy is often included on the ingredients label anyway. Cold-pressed oils (also called pure-pressed, expeller-pressed, or unrefined) are not safe to eat as they may contain significant levels of soy protein.

Soy is found in non-food products like cosmetics, nutritional supplements, medications and pet foods.

Infants and Soy Allergies

About 10-14% of babies who are allergic to cow’s milk develop an allergy to soy when given soy-based infant formulas. In the past, soy infant formula was used to treat cow’s milk allergy, lactose and galactose intolerance, and severe gastroenteritis. However the American Academy of Pediatrics in 2008 submitted new guidelines for the use of soy infant formula including the use of soy formula for full-term infants with galactosemia and hereditary lactase deficiency (rare), or for those families who prefer to follow a vegetarian diet. For infants with a cow’s milk allergy, an extensively hydrolyzed (the protein is chemically broken down) cow’s milk protein formula should be considered instead of soy formula because 10-14% of these infants will also have a soy allergy.

Eating Out with Soy Allergies

Eating out is very challenging with a soy allergy, so use good guidelines for dining out as much as possible. Many restaurants cook with soybean oil since it is an inexpensive vegetable oil and Asian restaurants use soy as a frequent ingredient on the menu.

Your best bet for eating out with a soy allergy is to choose a cuisine that does not traditionally use soy and to talk with the chef before you go to the restaurant. Because of the FALCPA exception for soybean oil and soy lecithin, foods listed as “soy-free” on chain restaurant websites may contain these ingredients.

More Helpful Tips:

Eating Vegetarian with a Soy Allergy

Eating a vegetarian diet with a soy allergy is an extra challenge. Most vegetarian convenience foods contain soy, although many newer vegetarian cookbooks avoid relying on soy as a protein source. Whole grains, legumes, and dairy products can help you to have a balanced diet and meet your protein needs.

Living with Soy Allergies

Since there is no cure for soy allergies at this point in time, living with a soy allergy means learning to avoid soy ingredients in foods and non-food items and being prepared for potential reactions.

You will need to carry an emergency first aid kit with you, including contact information, antihistamines, and an epinephrine auto-injector if prescribed by your doctor.


Joneja JV. The Health Professional's Guide to Food Allergies and Intolerances

Sicherer S. Food Allergies: A Complete Guide for Eating When Your Life Depends on It

Guidelines fro the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel.

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