Soy is one of the most common food allergens. Soy allergies are most common in children and young people. A child will usually outgrow a soy allergy, but the allergy may persist and be a lifelong condition.

A soy allergy is a type of food allergy — a condition in which a person’s immune system reacts to certain proteins in food as if they were harmful pathogens. When the immune system encounters these allergens, it overreacts and causes an individual to experience an allergic reaction.

A soy allergy can result in symptoms such as hives, vomiting, wheezing, and diarrhea. In rare cases, it may lead to anaphylaxis, which is a potentially life threatening reaction. In such cases, a person will need an epinephrine injection to treat the reaction.

In this article, we will discuss the risk factors, symptoms, and treatments associated with soy allergies.

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Soybeans, also known as soy or soya, are a popular variety of edible beans that are native to East Asia. They belong to the legume family, which also includes peanuts, peas, lentils, and other beans.

Soy and food products made from it are nutrient-dense sources of protein that are often popular in vegetarian and vegan diets. Soy is also a common ingredient in infant formulas and many other processed foods.

A soy allergy is one of the most common food allergies. Evidence suggests that more than 50 million Americans have some type of allergy and that food allergies affect 7.6% of children and 10.8% of adults. Most people will outgrow a soy allergy, but some may remain allergic to soy throughout their lives.

If the immune system recognizes soy proteins as a foreign substance, it may produce antibodies called immunoglobulin E (IgE). These antibodies trigger a person’s immune defenses when they encounter soy protein, usually causing a reaction within a few minutes or hours.

Soy allergy can cause different types of reactions that can be mild or very severe.

Mild soy allergy symptoms may include:

  • vomiting
  • stomach cramps
  • wheezing
  • diarrhea
  • swelling of the tongue and/or lips
  • hives

Severe soy allergy symptoms can include:

  • difficulty breathing
  • continuous cough
  • stiffness of the throat
  • weak pulse
  • pale/blue coloring of the skin
  • dizziness and/or confusion

In severe cases, a soy allergy can cause anaphylaxis, a serious reaction that can lead to a potentially fatal condition known as anaphylactic shock. This is when a person’s blood pressure drops very low and the blood has trouble circulating. It requires immediate medical attention and the administration of epinephrine.

When a person with a soy allergy encounters products containing soy, it triggers their immune system to overreact. There are two types of soy allergy: IgE-mediated and non-IgE-mediated.

IgE-mediated soy allergies

With this type of soy allergy, the body produces IgE. These antibodies mistakenly recognize soy proteins as harmful and respond by releasing chemicals, such as histamine.

This release of chemicals results in the symptoms that people experience during an allergic reaction. IgE-mediated reactions typically occur very quickly after a person consumes soy.

Non-IgE-mediated soy allergies

As the name suggests, this type of reaction involves other components of the immune system, rather than IgE. These reactions do not appear as quickly as IgE-mediated reactions and usually cause gastrointestinal symptoms such as vomiting, bloating, and diarrhea.

In rare cases, food protein-induced enterocolitis syndrome (FPIES) can occur. This is more common in infants. Because FPIES can result in severe diarrhea and vomiting that may lead to drastic fluid loss, it is important to seek immediate medical help.

Many foods contain soy or soy products. Soy is also a popular ingredient in many meat alternatives, as it is rich in protein. Examples of foods that are rich in soy include:

  • soy oil
  • edamame
  • miso
  • soy products, such as albumin, cheese, flour, ice cream, milk, nuts, sprouts, and yogurt
  • soya
  • soy sauce
  • tamari
  • tempeh
  • textured vegetable protein (TVP)
  • tofu

It is also possible to find soy in products such as:

  • canned broths and soups
  • canned tuna
  • cereals and crackers
  • cookies, biscuits, and baked goods
  • canned meat
  • high protein energy bars and snacks
  • infant formulas
  • low fat peanut butter
  • medications and personal care products
  • processed meats
  • sauces
  • sausages
  • soaps and moisturizers

It can be difficult to diagnose soy allergies because symptoms can vary and a person may not always experience the same symptoms during a reaction.

If a person suspects they have a food allergy, it is important to consult an allergist, who can perform tests to determine whether a person has an allergy. Once the allergist confirms the diagnosis, they will also be able to explain how to manage the symptoms and avoid exposure to the allergen.

To reach a diagnosis, the allergist will ask questions about the history, severity, and duration of the symptoms and the eating habits of the individual. They may then conduct the following tests:

  • Skin-prick test: The allergist places a drop of a liquid that contains the allergen on a person’s forearm or back. The doctor then pricks the skin with a sterile probe. If the test is positive, a small bump similar to a mosquito bite will be visible after 15–30 minutes.
  • Blood test: A blood test can measure the amount of IgE in reaction to specific types of food. The results usually take several days to become available.
  • Oral food challenge: After checking the results of the other tests, an allergist may wish to conduct an oral food challenge. This involves feeding the person gradually increasing amounts of the suspected allergen under the supervision of the doctor. Allergists can use this type of challenge to determine whether a patient has outgrown their food allergy.

Currently, there is not an effective treatment for the causes of soy allergies. Instead, it is advisable for a person with a soy allergy to try to avoid soy products. In case of a severe reaction, medications are available. Additionally, some people may outgrow the allergy over time.

Avoiding soy

To avoid an allergic reaction, it is crucial to read food labels and always ask about the ingredients in a meal before eating.

Because soy is one of the eight major food allergens, the law requires food manufacturers to adhere to specific labeling standards. According to the Food Allergen Labeling & Consumer Protection Act, food labels must declare allergens in an ingredient list or in a separate statement.


Epinephrine is the first-line treatment for anaphylaxis. As such, it is highly advisable for a person with a severe soy allergy to carry an emergency epinephrine kit with them.

Outgrowing soy allergies

Evidence suggests that roughly 50% of children with a soy allergy will outgrow it by age 7. This percentage goes up to 70% for children aged 10 and older. After a long period of no allergic reactions, an allergist may suggest an oral food challenge to determine whether the allergy is still present.

A soy allergy is a condition that causes people to experience an allergic reaction to soy proteins. This type of food allergy commonly affects children. Symptoms can be mild but, in rare cases, may lead to anaphylactic shock. An allergist can perform tests to determine whether a person has a soy allergy.

Some people may outgrow a soy allergy, but it can be a lifelong condition in others. To manage the condition, people should avoid soy products by reading food labels and should carry an epinephrine kit to avoid severe allergic reactions.