Soy Allergy: A Full Guide To Symptoms, Treatment, Management, & More

Soy Allergy 101: How To Handle This Common Food Allergy In Your Household

March 19, 2020 Updated July 9, 2021

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First things first, *hugs*. If you’re here, it means you or someone else in your household has a soy allergy. Maybe your child was recently diagnosed, and, let’s be real, food allergies are not one of those beautiful messes of parenthood that are good despite their inherent chaos. Food allergies are downright scary! We totally get your worry, hence, the hugs. You certainly aren’t alone — along with heavy-hitters like a milk allergy or egg allergy, soy allergy is one of the most common food allergies. That’s probably little consolation if your child is one of the approximately .4 percent of infants in the U.S. afflicted. Still, perhaps it will bring a modicum of comfort to know that many kids go on to grow out of soy food allergies. We’ll discuss that more in-depth further down, but first, we need to get to the nuts and bolts of what it means to have a soy allergy. What are the symptoms? How do you manage them?

To help you navigate all of these questions (and more), we gleaned as much insight into soy allergies as possible from medical health professionals and allergy experts. Keep reading to discover all of the ins and outs of this common food allergy so that you can keep your household soy allergy safe.

What causes a soy allergy?

We all know that the immune system is normally sort of a hero when it comes to human physiology. It fights off infection to help keep us healthy and strong. But when someone has a food allergy, the immune system goes off the tracks — for reasons unknown, it reacts abnormally and basically attacks the proteins in whatever food triggered it (as though those proteins were an infection).

When someone has a soy allergy, the protein their immune system overreacts to is in soy. And soy obviously comes from soybeans, which belong to the legume family. As you may well know, the legume family also includes another very common food allergen: peanuts (along with beans, lentils, and peas). Having said that, some people are allergic to only one legume and not others. In other words, just because your child has a soy allergy doesn’t necessarily mean they’ll be allergic to peanuts, too — and vice versa.

What does a soy allergy look like in a baby, toddler, child, teen, and adult?

One of the reasons a food allergy can be tricky to diagnose from the onset is because symptoms can vary so much from person to person. “Soy allergy or sensitivity can manifest differently depending on age,” Jamie Kim, certified dermatology physician assistant and founder of My Itchy Child, explained to Scary Mommy. “For babies, they might present as fussiness, diarrhea. For children and teens, it could be hives, vomiting, or diarrhea.”

What makes diagnosing soy allergies all the more complicated is that not only can they vary from person to person, but a single person might also exhibit different symptoms during every reaction. Per the American College of Allergy, Asthma & Immunology (ACAAI), allergic reactions to soy can affect:

  • The skin
  • The respiratory tract
  • The gastrointestinal tract
  • The cardiovascular system

Soy allergy symptoms at any age may include:

  • Vomiting
  • Stomach cramps
  • Indigestion
  • Diarrhea
  • Wheezing
  • Shortness of breath
  • Repetitive cough
  • Tightness in the throat and/or hoarse voice
  • Weak pulse
  • Pale or blue skin coloring
  • Hives
  • Swelling (that may affect the tongue and/or lips)
  • Confusion

How long does a soy allergy take to develop?

Like most allergic reactions to food, a soybean allergic reaction could very well be immediate. However, it could also be delayed and present hours after any exposure to soy or return for a second wave hours after the original reaction.

Although it is rare, a soy allergy can cause anaphylaxis, which is defined by the ACAAI as “a potentially life-threatening reaction that impairs breathing, causes a sudden drop in blood pressure, and can send the body into shock.” It’s more likely to occur in people who also have asthma or other severe food allergies. Symptoms of anaphylaxis, which require immediate medical attention, include:

  • Difficulty breathing, caused by swelling of the throat
  • Shock, accompanied by a severe drop in blood pressure
  • Rapid, weak pulse
  • Dizziness or lightheadedness
  • Loss of consciousness
  • Drooling and inability to swallow
  • Full-body redness and warmth (flushing)

The first and only line of defense against anaphylaxis is epinephrine, which is administered via an epinephrine auto-injector — also known as an EpiPen — as soon as any symptoms present.

How do you test for a soy allergy?

If you suspect you have a soy allergy, reach out to your primary care physician for a referral to an allergist. If you suspect your child has a soy allergy, you should immediately inform their pediatrician, who will likely also refer an allergist. To diagnose a soy allergy, the allergist will ask a comprehensive series of questions about the history of symptoms — this is why it’s an excellent idea to keep a journal to jot down notes anytime a reaction occurs. Typically, the allergist will pair the detailed questions with a skin-prick test and, possibly, a blood test (like the ImmunoCAP test) to indicate whether food-specific immunoglobulin E (IgE) antibodies are present in the bloodstream.

As a final step, your allergist may decide to do an oral food challenge, whereby suspected allergy-causing food is eaten in gradual increments to see how a person reacts. As you can imagine, this should only be performed by experienced medical professionals.

What foods should you avoid if you have a soy allergy?

Because soy is one of the eight allergens that fall under the labeling requirements of the Food Allergen Labeling and Consumer Protection Act of 2004, packaged food items sold in the U.S. that contain soy or a soy-based ingredient must be clearly labeled to reflect as much.

Per the ACAAI, soy or soy derivatives can be found in the following:

  • Some infant formulas
  • Canned broths
  • Soups
  • Canned tuna
  • Processed meats and hot dogs
  • Energy bars
  • Baked goods
  • Asian cuisine
  • Low-fat peanut butter
  • Alternative nut butters
  • Vodka
  • Many processed foods

Those with a soy allergy also need to steer clear of:

  • Soy milk
  • Soy yogurt or ice cream
  • Edamame
  • Miso
  • Tempeh
  • Soy sauce
  • Tofu
  • Any types of foods fried in oil are risky as well

In addition to “soy,” “soya,” and “soybeans” on food labels, be mindful that the following ingredients may also indicate a product contains soy:

  • Artificial flavoring
  • Natural flavoring
  • Glycine max
  • Hydrolyzed vegetable protein (HVP)
  • Hydrolyzed plant protein
  • Monodiglyceride
  • Monosodium glutamate (MSG)
  • Textured vegetable protein (TVP)

“Soy is found in many products, most of which the general public may not be aware. It is used to make Worcestershire sauce, some peanut butter, flavorings, broth, frozen meals, some Asian food, and meat substitutes like tofu,” explained Lisa Richards, nutritionist and author of The Candida Diet. “For a person with a known soy allergy, it is important to avoid these foods. It is in so many products that it can be difficult to avoid, making it all the more important to know how to spot it in foods or recipes.”

People with soy allergies are generally okay to consume highly refined soybean oil as well as foods that contain soy lecithin, but you should always consult an allergist to find out if a food is safe before trying it.

Can you be allergic to soy sauce but not soy?

Yes! If you experience a reaction after eating soy sauce but are generally fine with other products that contain soy, it’s likely another ingredient that’s triggering an immune response. While soy is right there in the name, the tasty sauce also includes other common allergens, including wheat.

Wheat is one of the eight most common food allergens, alongside eggs, soy, cow’s milk, peanuts, tree nuts, and fish. So, if soy doesn’t generally bother you, but you do become bloated, itchy, or ill when you consume other wheat products, then it’s the wheat that is most likely to blame. If you simply can’t imagine cooking without soy sauce, try looking for a gluten-free version like tamari soy sauce the next time you’re whipping up something that needs an extra punch of umami. Even though having a wheat allergy is frustrating, it’s much easier to find soy sauces that don’t contain wheat than it is to find ones without soy.

Does soy intolerance cause inflammation?

First of all, it should be noted a food intolerance isn’t the same as a food allergy, even if the terms are sometimes used interchangeably. Generally, allergies develop early in life, while an intolerance can occur at any time, including adulthood. Additionally, food intolerances are not life-threatening (unlike allergies) — but they are uncomfortable. An intolerance usually causes symptoms like:

  • Bloating
  • Stomach cramps
  • Nausea
  • Gas
  • Diarrhea

So, it’s definitely not a fun situation in which to find yourself. In the case of soy intolerance, all of those stomach issues can lead to inflammation if you continue to consume products with soy in them. Then, in turn, inflammation leads to diarrhea, as reported by LiveStrong. It’s a truly frustrating cycle, and unfortunately, the only way to figure out if you have a soy intolerance is to keep a food diary and try an elimination diet. As you may have guessed, your doctor should be your first port of call if you suspect you have a food intolerance.

There’s currently no foolproof test for food intolerances, so figuring out what foods are making you feel ill is a case of trial and error. But, at the very least, it’s good to know that food intolerances aren’t life-threatening, and if you do have one, you don’t have to eliminate soy from your diet entirely. (Although, the less of it you eat, the happier your stomach will be in the long run.)

What is a good substitute for soy?

Soy is in a surprising amount of foods. From Worcestershire sauce to canned tuna, if you’re avoiding soy, it may seem like it’s everywhere. But even if you’re navigating a food allergy, there are ways to still enjoy tasty meals by making easy swaps at home. Below is a list of foods you can substitute in recipes that call for ingredients with soy:

  • Canola oil
  • Kosher for Passover margarines
  • Coconut aminos sauce (a terrific soy sauce alternative)
  • Non-soy miso pastes
  • Dried mushrooms
  • Black beans, kidney beans, and other legumes
  • Almonds, cashews, and other nuts
  • Pumpkin seeds
  • Plant-based milks
  • Beyond burger (perfect for vegans)

Granted, you should always double-check the ingredients label. And there are going to be cases where recreating a dish sans soy may not be possible — that’s the unfortunate reality of living with food allergies. But when that happens, just remember to be flexible, choose something that you and your whole family can safely enjoy, and focus on all of the tasty foods that are still available to you.

What are the risk factors?

According to the Mayo Clinic, there are a few factors that could play a part in putting your child at greater risk of developing a soy allergy. These include:

  • A family history of allergies to soy or other foods.
  • A family history of other allergies — “It’s not well understood if soy allergy itself is genetic, but soy allergies are commonly seen in people with atopic dermatitis (eczema), which can be genetic,” Kim told Scary Mommy.
  • Age — Soy allergy is most common in infants and toddlers.

Do soy allergies ever go away?

Allergic reactions to soy typically first appear in infants and kids under three. And while there are no guarantees it will go away, many children do outgrow the allergy over time. Per Kim, “About 50 percent of children outgrow soy allergies around seven years of age and many outgrow by 10 years old.”

Are there any soy allergy treatments?

For kids, there’s a good chance that they’ll outgrow a soy allergy before they turn 10. However, if you’ve reached adulthood and you still have a soy allergy, then it’s just something you’re going to have to continue to manage. The only actual treatment for soy allergies is avoiding products that contain soy.

If you accidentally end up eating something that contains soy, then you may be able to mitigate your allergic reaction with antihistamines. But this is only recommended if your allergy is mild. If you have a severe reaction to soy, you may need an epinephrine injection, and you should definitely seek immediate medical attention. Ultimately, having a soy allergy means you’re going to have to be hypervigilant about the foods that you or your child eats, because there’s simply no true treatment available just yet.