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A detailed overview of soy allergies. What signs to look for, how to avoid it, and how to treat it if you're experiencing a reaction.

Soy is derived from soybeans, and it triggers one of the most common food-related allergies spread on a worldwide level. Soy allergy can have its roots way back in a person’s infant years when soy-based infant formula is administered to the little ones. There are a lot of children that outgrow their soy allergy, but some are not so lucky.

What causes soy allergies?

This specific type of allergy is triggered by soy protein, which acts as the allergen. The body considers soy proteins to be a threat and start reacting accordingly in order to block it. As the immune system overreacts to this trigger, it releases antibodies to help fight it off. These antibodies will stand by and be prepared for the next “soy attack”, ready to release chemicals into your bloodstream. This is when the allergic reaction signs become visible.

Children are the ones most exposed to developing soy allergies. It usually takes a few hours after consuming soy or other products that contain soy protein for the symptoms to appear. This food protein-induced enterocolitis syndrome has a long-term solution, unlike other types of food allergies. 

People who are looking to prevent a soy allergy, need to know about the exact proteins that could trigger this reaction. Parents that tend to feed their babies with soy-based formulas might consider switching to breastfeeding, in case the child displays symptoms of what might be a soy allergy. 

Soy is a common ingredient in many foods, so avoiding it can be more complicated than it seems. Unexpected foods, such as peanut butter, canned soups, and even bakes good, could contain traces of soy protein. If you’ve purchased a product once, make sure to read its label every time you do so, as the list of ingredients may change.

While there are a few minor exceptions to the rule, pretty much every label that has the word “soy” written on it should be avoided, particularly: vegetable oils, soy sauces, natto, miso, tofu, and any soy-based products (like milk, yogurt, ice cream, flour, cheese, etc.). 

What are some common symptoms?

  • Skin flushing
  • Abdominal pain
  • Vomiting
  • Hives
  • Breathing problems
  • Swelling

Soy is one of the eight major foods that fall under mandatory labeling regulation instated by the Food Allergen Labeling and Consumer Protection Act of 2004. That’s because it’s one of the main foods related to allergies. The good news is that, compared to the other foods in the group, soy allergy is rarely life-threatening.

The symptoms related to this allergy are more uncomfortable than anything, and may include: skin flushing, abdominal pain and related discomfort (nausea, vomiting, diarrhea), runny nose or troublesome breathing, skin irritations (in the form of eczema, itchiness, and hives), swelling of different body parts, and mouth tingling sensations.

In some extreme cases, people can experience anaphylaxis, which is accompanied by symptoms such as dizziness, throat swelling, major blood pressure drops, rapid pulse, and even loss of consciousness. If you or someone around you experiences an anaphylactic shock, the first rule is to administer an adrenaline injection, followed by an emergency 911 call.  It’s very important to administer the epinephrine injection first. Failure to do so increased the chances of heart failure. 

Diagnosis & treatment

A doctor will follow a series of steps in order to determine if a person is suffering from a soy allergy or not. They will ask questions about a patient’s medical history, as well as current food habits, and symptoms that may occur after eating certain ingredients. The skin prick and blood test are next steps, but these often turn out inconclusive. On a general note, food allergies are quite difficult to diagnose, as their symptoms are almost identical to one another. 

If both of these tests fail to deliver a response, doctors may turn to either the food challenge or the elimination diet. The first one implies live testing of a patient’s reaction when coming in contact with the suspected allergen (and, of course, curing any temporary symptoms that an allergy might trigger). The second test takes longer to perform, as it implies eliminating the suspected ingredient from the patient’s diet, and the reintroducing it to examine the potential body responses. 

As every doctor will tell you, the most important thing when living with a food allergy is to avoid consuming the trigger. With soy, it’s not that easy. You might consume products that contain this ingredient without even knowing it. There are some over-the-counter options that might help in case of an allergic reaction to soy. The most popular antihistamines recommended in such a situation are: 

  • loratadine,
  • chlorpheniramine,
  • diphenhydramine. 

Soy substitutes

The good thing about soy is that, if you have an allergic reaction to it, you can replace it with similar, allergen-free options. For example, soybean paste has rice and bean alternatives, but they are only viable if you don’t suffer from another bean-related allergy. Statistics show that five percent of the people who have a legume reaction (such as soybean), will be allergic to other legumes as well. People that are huge fans of soy sauce, can replace it with some of these alternatives: balsamic vinegar, olive brine, or even miso sauce that doesn’t contain any soy. 

What’s interesting is that refined soy oils are generally safe for people who have soy allergies. It’s a common ingredient in many salad dressings. That’s because the refining process reduces the amount of protein that can trigger an allergic reaction. 


Soy is one of the richest sources of protein in a child’s diet. Soybeans have other important vitamins and minerals, such as vitamin B6, zinc, calcium, riboflavin, magnesium, and others. If soy has to be eliminated from your child’s diet, you can supplement the missing proteins and vitamins with vegetables, fruit, and fortified grains. But before that, make sure that your child doesn’t have any other allergic reactions, especially to milk, fruit, and eggs.

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