Are You Allergic to Soy?

According the American Academy of Allergy, Asthma and Immunology, soy is among the most common of food allergens.  Next to wheat, dairy, eggs and peanuts, soy is among the top five of food allergens.  The part of any food that usually causes an allergic reaction is the protein portion of the food. Thus, the protein found in soy is what causes the allergic reactions.  In fact, there may be up to fifteen different proteins in soy that can cause allergic reactions and even a gene that may be responsible for up to 75 percent of the allergic reactions. (1)The allergy to soy can be mild for most and life-threatening for some.  Some of the symptoms that may be experienced are:

Hives •   Diarrhea

Eczema •   Abdominal cramping

Skin conditions •   Colic in babies

Wheezing and asthma •   Abdominal swelling

Bloating •   Gas

Nervous system irritation •   Itching

Chest tightness •   Abdominal pain

Hay fever-like symptoms •   Mouth sores and itching

According to the National Institute of Allergy and Infectious Diseases, soy allergies are particularly common in infants and young children. But, the allergy may show up at any time and may show up in foods that have been previously eaten without problems. 

It is very difficult to avoid eating soy!  It is one of the top four subsidized crops and therefore inexpensively and readily used by food manufacturers. On top of that, there has been great media exposure on the health benefits of soy.  But, the reality is that it is a common food allergen and for those who are sensitive to soy, strict avoidance is the only way to prevent a reaction.  Thus, purchasing foods and food products takes vigilance and awareness as hidden soy exists in thousands of foods and cosmetics.  Even “cardboards, paints, cars, biodiesel fuels, fabric softeners, mattresses and books contain soy.” (2) 

In 2004, the Food Allergy Labeling Consumer Protection Act was passed. It required that food manufacturers clearly state whether a product contains any of the top allergens.  But, some of manufacturers can hide the soy in vitamin E, lecithin and soy oil as these are not required to be listed on labels. Additionally, consuming meat from animals that have been fattened with soy feed may cause allergic reactions in those who are highly sensitive. 


Some people with a soy allergy may have reactions after eating other foods from the legume family such as peanuts, kidney beans, lima beans, pinto beans, string beans, garbanzo beans, lentils, peas, black-eyed peas and licorice. There also may be a cross-reactivity to birch pollen. This is not as common and is usually found in those with the most reactivity to soy. But, if you suffer any symptoms when eating legumes, you may want to consider that it may not be just a digestive issue, but a sensitivity or allergy to the legume family of foods.

Avoiding Exposure

These are the foods that contain soy and must be avoided.

Edmame (soybeans) •   Miso

Soy sauce •   Natto

Tofu •   Soy nuts

Tempeh •   Soy protein in protein bars

Soy flour •   Soy milk

Soy ice cream •   Shoyu sauce

When reading labels look for soy, soya or soybeans, either in bold print or following the ingredient list after the word “contains.”

The following is a list of foods and food preparations that commonly contain soy or soy derivatives:

Soy oil •   Pancake flour •   Margarine

Tamari soy sauce •   Soy protein isolate •   Sauces

Sausages •   Vegetable protein •   Gravies

Marinades •   Salad dressings •   Seitan

Teriyaki sauce •   Soups •   Vegetable protein

Hydrolyzed and textured •   Asian foods •   Lecithin *

vegetable protein •   Artificial flavoring •   Vegetable broth

Vegetable gum •   Infant formula •   Bouillon cubes

Canned chicken broth •   Nutritional supplements •   Soy protein powder

Oyster sauce •   Breads •   Doughnuts

Pancake mix •   Canned tuna (some) •   Vegetable starch

Probiotic supplements •   Soy yogurt •   Vegan burgers

Medications (Benadryl •   Hot dogs •   


Please check the labels thoroughly!

Soy protein isolate used in the manufacture of paperboard boxes can flake off and migrate into food. In the future, some foods may be shrink-wrapped in an edible soy-based plastic.

Is Soy Oil or Soy Lecithin OK?

There has been some recent controversy over whether soybean oil and soy lecithin actually contain the soy protein. Soybean oil goes through a process to make it more fluid.  In that process hexane is used leaving a gummy residue called lecithin. The lecithin is then dried and bleached.  It is then sold to food manufacturers, cosmetic companies, supplement manufacturers and health food stores. Both soybean oil and lecithin do contain small amounts of soy protein and an enzyme inhibitor that may cause allergic reactions.(3) 

Soybean oil is used extensively in salad dressings and lecithin is found in many packaged foods, protein bars and as a fat emulsifier in all sorts of food items from chocolate bars to ice cream. Lecithin is a good source of choline which is an essential part of every cell membrane. It also aids memory and cognitive function as well as fat metabolism. A study, published in the Journal of Clinical and Experimental Allergy tested soybean sensitive individuals for reactions to soybean oil and soy lecithin. The study concluded that even though these products were produced from extracts of soybeans that it was exceedingly rare for the participants in the study to suffer a reaction to these soy bean derived products.(4) 

Since there are conflicting opinions and research, I would caution those of you with the more severe reactions to soy to also stay away from soybean oil and lecithin. It may be that those people who do not have severe soy allergies may consume lecithin and soy oil as it may be less problematic for them. It just requires personal attention and further investigation as well as taking note of any reactions.

The real problem with soy oil is that it is used in deep frying foods and on the griddle where it becomes a damaged fat.  Damaged fats can cause free radicals and inflammation.

What Are Other Mechanisms for Soy Reactions?

Soybean trypsin inhibitor has also been identified as an allergen.(5) Whenever there is a damaged intestinal lining or “leaky gut”, soy lectins can easily pass into the bloodstream, triggering allergic reactions.  Lectins are a special class of protein molecules found in the body and in food.  Some allergic responses are actually reactions to lectins.  Wheat germ agglutinin has been known to cause constant immune stimulation leading to intestinal permeability. Lectins can therefore cause damage to the gut.(6)

Because soy infant formulas are used as substitutes for cow’s milk formulas, a study was conducted to determine if there is a cross reaction between casein from cow’s milk and the proteins in soy. The study used blood samples from cow’s milk allergic patients who had not previously been exposed to soy.  The researchers concluded that ”soy formula could be involved in allergic reactions observed in cow’s milk allergic patients exposed to soy-containing foods.  Altogether our results suggest that the highly allergenic caseins cross-react with the B3 polypeptide from the 11S globulin of soybean. This in vitro cross-reactivity should be considered when milk allergic patients are treated with soy-derivatives.”(7)

Eating Out

In order to avoid eating a hidden food allergen, when you eat out you will need to ask about the ingredients. It is not uncommon for many fast food chains to use soy flour in their bread products or soy derivatives as fillers for their meat dishes. McDonald’s and Burger King list soy flour as an ingredient in their hamburger buns. Carl’s Jr. adds soy protein as a filler in its Philly Cheese Steak Sandwich. Stir frying or serving marinades made with soy sauce is a staple at many restaurants, particularly Asian restaurants. This is not to say that you shouldn’t enjoy eating out, but just to remind you to exercise caution when ordering your favorite dishes.

Eat Wholesome Fresh Food!

Eat wholesome fresh foods and you won’t have to be frustrated by poring over food labels. You can prepare nutritious foods and never have to be concerned about inadvertently consuming any soy. 


1. Soy Allergy, retrieved on June 30, 2009 at

2. Daniel, K. Part I – A Strategy for Dealing with Soy Allergies, retrieved on June 20, 2009


3. Xuelin, G. Identification of IgE-Binding Proteins in Soy Lecithin, International

Archives of Allergy and Immunology, 2001; Vol. 3, No.126:218-225.

4. Awazuhara, H. Antigenicity of the proteins in soy lecithin and soy oil in soybean

allergy, Journal of Clinical and Experimental Allergy, December, 1998; 28(12):1559-1664.

5. Burks, AW, Identification of peanut agglutinin and soybean trypsin inhibitor as minor legume allergens, Int Arch Allergy Immunol, Oct. 1994, 105(2):143-9.

6. Cordain L, Toohey L, Smith MJ, Hickey MS. Modulation of immune function by dietary lectins in rheumatoid arthritis. Br J Nutr. 2000 Mar;83(3):207-217.

7. Rozenfeld, P. Detection and identification of a soy protein component that cross-reacts with caseins from cow’s milk, Clin Exp Immunol, Oct. 2002, 130(1):49-58.