Symptoms of a Soy Allergy & Sources of Soy

Just as with peanut allergies, soy allergies are not to be taken lightly.

“If you have an allergy to soy, it means that your body has misidentified any or all of the 15 or so proteins in soy as dangerous substances,” explains Deborah Krivitsky, a registered dietician, and director of clinical nutrition at the Massachusetts Cardiovascular Disease Prevention Center at Massachusetts General Hospital in Boston. “When you eat anything that contains soy, your body reacts by releasing an antibody that sends out a team of chemicals to combat the soy allergens. The way your body reacts to the chemicals it releases is what dictates the types of allergic symptoms you suffer.

According to Krivitsky, soy allergy symptoms may include:

* tingling in the mouth

* hives

* itchy, scaly skin (eczema)

* swelling of lips, face, tongue and throat or other parts of the body

* wheezing

* trouble breathing

* runny nose

* abdominal pain, diarrhea, nausea, vomiting

* redness of the skin (flushing)

A severe allergic reaction to soy – called anaphylaxis – is rare, says Krivitsky, and is more likely to occur in people who have asthma or who are also allergic to other foods, such as peanuts. Anaphylaxis causes these more extreme symptoms:

* constriction of airways, including a swollen throat or a lump in your throat that makes it difficult to breathe

* shock, with a severe drop in blood pressure

* rapid pulse

* dizziness, lightheadedness or loss of consciousness

Soy allergy in infants often begins with the introduction of a soy-based formula. A soy allergy may develop when a child is switched to a soy-based formula after an allergic reaction to a milk-based formula.

To prevent allergic symptoms to soy, your best bet is to avoid soy and all products containing soy, and to read the labels of packaged foods. “The ingredient list might mention soy, soya, soybeans or glycine max,” says Krivitsky. “In addition, the Food and Drug Administration requires food producers to print a warning on the label of any food that contains soy. However, the label won’t necessarily say whether the food was made in a facility that also processes soy even when it might. 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.”

Krivitsky’s other tips:

* 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. If you can’t be certain that 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 any place with communal grills (like hibachi restaurants). Buffets also can be risky since utensils may be moved from one food to another.

* Talk to the staff at your child’s school about cross-contamination risks for foods in the cafeteria. It may be best to pack lunches from home.


Go to the next page to read about foods that contain soy.


Soy Sources

Krivitsky lists the following sources of soy, along with a description of each:

Miso soup, a common Japanese staple found in American Asian restaurants. Miso soup is made with miso paste and additions of tofu and vegetables, such as carrot or daikon radish. Miso paste is typically made from fermented soybeans. Other ingredients such as barley, buckwheat, millet and rye may be used to make miso soup, as well.

Tamari is also made from fermented soybeans with the addition of wheat-like soy sauce, but tamari contains more soybeans and less wheat in its production. This makes tamari thicker and less salty than soy sauce.

Shoyu sauce is a natural soy sauce made from soybeans, roasted hard red wheat, sea salt and water. It is less salty and thicker than commercially prepared soy sauce. The time allowed for fermentation varies the flavor quite a bit.

Vegetable broth, gum, or starch: In the production process, broths may be flavored with soy sauce, and gum or starches may contain soy flour. Check with the manufacturer.

Tempeh is made from cooked and fermented soybeans which are shaped into a patty, like a firm veggie burger. Tempeh has a nutty flavor.

Teriyaki sauce usually contains soy sauce as one of the ingredients, which indicates the presence of soy allergen. Teriyaki sauce has garlic, ginger and sugar, as well.

Low-fat peanut butter: Soy protein is added to boost the protein content and help with emulsification (emulsifiers keep the ingredients mixed together, like oil and water, and the fat from rising to the top of the peanut butter jar).

Natto is a Japanese health food made with fermented soybeans and beneficial bacteria.

Natural flavors are flavor additions to products that may contain soy ingredients. You should always check with the manufacturer about what constitutes “natural flavors” if you are unsure.

Energy bars: Soy protein isolate may be included as a way to boost the overall protein content (and it’s inexpensive) in energy bars. Soy lecithin may be added as an emulsifier.

Protein powder: This is an umbrella term for many different sources of protein. You may find milk (whey and casein protein), rice and many other foods providing the source of protein. Soy protein powder is a popular protein powder source found in grocery and health food stores, and it comes from soy beans. Be sure to read ingredient labels so you know the type of protein powder.

Hamburger meat and buns: Some fast food restaurants include soy flour in their buns and soy protein as an extender in the beef they use to make hamburgers. Make sure you understand the requirements for fast food and chain restaurants regarding food allergen labeling.

Meat alternatives: “Chicken” nuggets, veggie burgers and hot dogs may be made with soy protein or tofu.

Deli meats: Hydrolyzed soy protein may be present to enhance the flavor of deli meats.


Read our article "The Truth About Soy" here.

Mary Alice Cookson is associate editor of Boston Parents Paper.

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09 Jul 2014

By Mary Alice Cookson