What Is A Soy Allergy?

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A soy allergy occurs when the immune system mistakes the protein in soy as a threat to the body and reacts to attack it. This causes symptoms like rashes, stomach pain and trouble breathing. In rare cases, soy can cause anaphylaxis. This serious, potentially life-threatening reaction is more likely to occur in those who have asthma or other food allergies in addition to a soy allergy.

Soy, also known as soya or soybeans, is a legume. Having a soy allergy is among the more difficult food allergies to manage because soy is in many processed and prepared foods. Soy is a common trigger of food protein-induced enterocolitis syndrome (FPIES) or a delayed food allergy that affects the gastrointestinal tract. Symptoms include vomiting, diarrhea and dehydration, which usually occur within hours of eating the allergen rather than minutes. 

When are soy allergies discovered?

Soy allergies are most common in infants and toddlers and are often discovered when the child reacts to soy-based formula. Many children outgrow a soy allergy by age three with the majority outgrowing it by age 10. Few continue to be soy allergic into adulthood. Those with multiple allergies to wheat, beans, milk or other foods have a greater chance of being allergic to soy.

If you have an infant, consider breastfeeding or using hypoallergenic formula instead of a soy or milk-based formula. Speak with your pediatrician or allergist about the best options for your child.

How to avoid soy

Avoiding soy can be difficult as it is a main ingredient in many processed foods like meat, sauces, breads, etc. Staying informed about ingredients and taking precautions against accidental soy consumption is key to avoiding an allergic reaction. Some people with soy allergies may not react to soy lecithin, a widely used food additive that acts as an emulsifier in foods like chocolate, peanut butter and margarine. Discuss with your doctor whether it is a safe option for you. 

When dining out, be careful about eating foods that have been fried in oil, due to the risk of cross-contamination. Avoid food that has a thick, gooey or creamy texture, which often contains soy, an emulsifier. Thick sauces in Asian cuisine, the cream in Oreos and frosting in desserts are a few culprits. Also watch out for anything bound together, like burgers, as soy is often used as a binding agent. As a rule of thumb, the less processed and simpler the ingredient list, the better.

Another common question is whether or not people with soy allergies can eat other legumes such as lentils or beans. According to studies, 95% of people with allergies to one legume can generally consume other legumes. Consider undergoing food allergy testing to better understand what foods you can safely eat and what allergens you should avoid.

Because soy is one the Top 8 allergens, the federal government is required to clearly list soy as an ingredient on food products. Learn how to read a food label for peanut ingredients before consuming packaged food, and be sure to always check for precautionary β€œmay contain” statements with cross-contamination warnings. Note that manufacturers are not legally required to label for potential cross-contamination.

Soy can often be found in:

  • Asian cuisine

  • Canned broths and soups

  • Canned tuna and meat

  • Baked goods

  • Cereals

  • Cookies

  • Crackers

  • High-protein energy bars and snacks

  • Infant formulas

  • Low-fat peanut butter

  • Processed meats

  • Salad dressings

  • Sauces

  • Vegetable broth

  • Vegetable gum

  • Vegetable starch

Foods to avoid:

  • Soy (soy milk, soy cheese, soy flour soy ice cream and soy yogurt)

  • Tofu

  • Edamame

  • Miso

  • Natto

  • Shoyu

  • Soya

  • Soybean (curd, granules)

  • Soy protein (concentrate, hydrolyzed, isolate)

  • Soy sauce

  • Tamari

  • Tempeh

  • Textured vegetable protein (TVP)

Non-food products that could have soy

In beauty, skin and hair care products, soy is sometimes listed in ingredients as: glycine soja oil, glycol distearate, hydrogenated lecithin, hydrolyzed vegetable protein, lecithin, and tocopherol. Note that FDA food label rules do not apply to non-food products.

Alternative names for soy:

  • Soya

  • Soybean

  • Glycine max

  • Dolichos soja

  • Hydrolyzed vegetable protein (HVP)

  • Textured vegetable protein (TVP)

  • Monodiglyceride

  • Monosodium glutamate (MSG)

Soy substitutes

Consider using rice-based and coconut-based alternatives if you need to avoid milk and soy. Edamame or whole soybeans can be swapped with other beans such as fava and chickpeas.

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