Tofu and other soy products can trigger allergies in people who have soy allergies.

USDA Agricultural Research Service (Scott Bauer)

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Soy Allergy

Overview:

Soy is one of the so-called "big eight" allergens, and along with milk allergies and egg allergies, it is one of the three allergies children are most likely to outgrow. While soy per se is not that prevalent in the American diet, it is used in a wide variety of processed foods and in East Asian cuisine, making it challenging to avoid. It is also a staple protein in many vegetarian households; vegetarian families dealing with soy allergies will perhaps find this allergy more challenging than other households.

Soy Allergy Symptoms:

Most soy allergies are fairly mild and may cause hives, nausea, or rhinitis. Soy rarely causes severe reactions, including breathing difficulty and anaphylaxis. Severe reactions are most likely in people who also have peanut allergies and asthma.

Food Protein Induced Enterocolitis Syndrome, which is not a true allergy but an intolerance, is a rare disorder affecting infants and toddlers drinking soy formula. Its symptoms include diarrhea, vomiting, and dehydration, and treatment consists of avoiding the offending food.

Soy is also a trigger of the oral allergy syndrome, which causes itching in the mouth.

Cross-Reactivity:

There are two major cross-reactivity concerns with soy. The first is between soy and birch pollen. The protein that causes this cross-reaction has been linked with the oral allergy syndrome (described above). Another concern for families with soy allergies is allergies to other legumes, especially peanuts. Most people with soy allergies do tolerate peanuts, peas, and other legumes, however.

Special Concerns for Formula-Feeding Infants:

Soy formula is widely available and is commonly used to feed infants who are not breastfed and who are unable to tolerate cow's milk-based formulas. Some families are concerned about putting children at risk for peanut allergies by feeding them soy formula, but a 2005 study showed no increased risk.

However, soy formula is not considered optimal for children at high risk of developing allergies. High-risk children include those with at least one relative with a doctor-diagnosed food allergy. Hypoallergenic formulas are considered a better choice for these babies, along with a late introduction to solid foods.

Soy Allergies and Labeling Laws:

Soy is covered by FALCPA, which is the Food Allergen Labeling and Consumer Protection Act. This law requires that the presence of soy be listed in plain English as "soy," "soya" or "soybean" on labels, either in bold print in the list of ingredients or following the ingredient list after the word "Contains."

It's still useful to learn different names soy may appear under in an ingredient label. Be especially aware of the word "vegetable" in the context of the word "protein" or "starch;" if unspecified in a product that you see in a non-consumer setting (a restaurant kitchen, for example), this could indicate soy.

Eating Out with Soy Allergies:

The basic rules for eating out with food allergies apply. You'll probably want to call the restaurant ahead and discuss your dietary restrictions. In general, the fewer processed foods a restaurant uses, the greater your chances of finding a safe food.

While soy sauce can make many Asian cuisines challenging, sushi may be one of your safest options (just avoid eel and any other dishes with sauce already on them). In all restaurants, be wary of anything cooked on a communal grill where any dishes have been marinated in soy-based marinades; this is a high-risk situation for cross-contamination.

Soy Oil and Soy Lecithin:

For many people, soy oil and soy lecithin (a common emulsifier) are considered to be of little to no consequence with respect to allergies because they include very little protein. But both of these ingredients have been known to cause allergic reactions in rare instances.

There are two reasonable options to address these common foods. One is to discuss the risks and benefits of using them in a soy allergy diet (and possibly to arrange additional allergy testing) with your allergist. The other is to accept that they are in a variety of foods, and avoid them nonetheless.

Foods Commonly Containing Soy:

Some foods always contain soy. These include edamame, shoyu, tamari, tofu, tempeh, miso, and natto. Soy is also sold on its own as "soy nuts" and used as a health food in cereals and meal replacement bars. If you see isoflavones advertised on a health food, look out for soy on the label.

But soy is present in a dizzying array of processed foods, often in the form of textured vegetable protein (TVP), hydrolyzed vegetable starch, soy flour, or lecithin (as mentioned above). Foods that are particularly likely to include soy include salad dressings, soups, sauces, margarine, and vegetarian meat substitutes.

Special Concerns for Vegetarian Families:

Vegetarian families with soy allergies will face several challenges, including having to avoid many convenience foods. Many vegetarian cookbooks, too, rely on tofu and soy products.

If you enjoy soy foods' texture, try seitan. (Some commercial varieties may include soy, so read labels). If not, you can get protein from beans, corn, and whole grains. See Vegetarianism and Food Allergies for more about soy-free vegetarian diets.

As for cookbooks, I recommend Anna Thomas's The New Vegetarian Epicure. Based on Mediterranean and Eastern European cuisine, it uses no tofu or edamame, and only minimal soy sauce.

Living with Soy Allergies:

The biggest problem with most soy allergies isn't replacing soy in the diet; while soy is healthful, most North Americans (unless they're vegetarians) don't eat so much tofu, tempeh, or soymilk that they will find it tremendously difficult to replace. (If you are worried about replacing soy in your diet or your child's diet, it's a good idea to ask a nutritionist or dietitian for advice.) Instead, the major challenge for Americans with soy allergies is avoiding soy in processed foods.

Reading labels is paramount with a soy allergy. Because soy is used as a flavor enhancer, a "stretcher" for meats, and a flour, it can appear in virtually any kind of food, from ice cream to hamburgers to clear broths. While you can find some allergy-safe products at your grocery by checking labels carefully, you may be able to find more online at a store like Kids Allergy Stop.

As noted above, most soy allergies are mild, and pose little risk of anaphylaxis. However, if your allergist prescribes an Epi-Pen or other form of injectible epinephrine, you should carry it with you at all times and learn how to treat anaphylactic shock. Because soy allergies are riskiest in people with asthma, it's wise to make sure you're managing your asthma as well as you possibly can if you have both conditions.

_Sources:

Awazuhara, H. "Antigenicity of the Proteins in Soy Lecithin and Soy Oil in Soybean Allergy." Clinical and Experimental Allergy. Dec. 1998 28(12): 1559-64.

Høst, A., S. Halken. "Hypoallergenic Formulas – When, To Whom, and How Long: Finally, After More Than 15 Years We Have The Right Indication!" Allergy Aug. 2004 59(s78): 45-52.

Kleine-Tebbe, J., et al. "Severe Oral Allergy Syndrome and Anaphylactic Reactions Caused by a Bet v 1- Related PR-10 Protein in Soybean, SAM22." Journal of Allergy and Clinical Immunology. Nov. 2002 110(5): 797-804.

Moneret-Vautrin, D. A. et al. "Unusual Soy Oil Allergy." Allergy. Mar. 2002 57(3): 266-67.

Pereira, M.J., et al. "The Allergenic Significance of Legumes." Allergologia Immunopathologia. Nov.-Dec. 2002 30(6): 346-53.

Sicherer, S.H., Hugh A. Sampson, A. W. Burks. "Peanut and Soy Allergy: A Clinical and Therapeutic Dilemma." Allergy. June 2000. 55(6): 515-21.