Soy Allergy – Causes, Signs and symptoms

Soy allergy

Also called: Soy Bean Allergy

Summary

Soy allergy is an allergic reaction to soybeans and foods that contain ingredients derived from this legume. Products that contain soy – including some inks, soaps and cosmetics – can also cause reactions.

Soy allergy is most commonly found in infants and only rarely in adults. Symptoms include a wide range of reactions, from nasal congestion to bronchospasm (sudden tightening of the airways) and anaphylaxis(a dangerous allergic reaction involving two or more body systems).

Soybeans are high in protein, making soy products popular for vegetarians and other people seeking meat alternatives. Avoidance of soy-based foods and ingredients is the only certain way to prevent symptoms related to soy allergy.

About soy allergies

Soy allergy is a reaction to foods, ingredients and products derived from soybeans. It can provoke a wide range of symptoms, which range from nasal congestion to potentially more serious manifestations such as bronchospasm (sudden tightening of the airways) and anaphylaxis (a dangerous allergic reaction involving two or more body systems). 

Soybeans are legumes (pods or seeds used as food) that can be found in many foods and food products, including vegetable oils, soy sauces and tofu. Soy is an allergen for some people. Because soy is present in so many foods, those who are allergic to it must be very careful to become familiar with soy-based products and ingredients. Avoidance is the only technique certain to prevent symptoms.  

Soy allergy is more common in infants than any other group. It often appears in the first three months of life, and disappears by the time a child is 2. Soy allergy symptoms are rare in adults.

Soy milk was once considered a good alternative for infants who could not drink regular milk or were at increased risk of food allergies. However, as more and more infants switched to soy milk formulas, it became clear that soy, too, was a major food allergen (though there is no cross-reactivity between cow’s milk and soy – each triggers an allergic reaction independently). For this reason, soy formulas are no longer considered a safer type of formula for at-risk infants.

Laboratory research has had some success with the creation of allergen-free varieties of soybeans. While they have not yet been adopted by the marketplace, allergen-free soybeans could one day begin to replace the allergy-causing lines currently being grown.

Potential causes of soy allergy

Soybeans are legumes (a pod or seed used as food) that can be found in many different products. Soy can be consumed in plant form or as a substance added to food products, such as vegetable oils or soups. Soy is also used in a variety of non-food products, such as inks, soaps or cosmetics. In some people, contact with these soy products will result in an allergic skin reaction called atopic dermatitis.

People with soy allergies may have cross-reactions to other legumes, including:

  • Peanuts
  • Green peas
  • Chick peas
  • Lima beans
  • String beans
  • Navy beans
  • Kidney beans
  • Black beans
  • Pinto beans
  • Lentils
  • Carob
  • Licorice

In addition, many foods and ingredients contain some type of soy product. These include:

  • Hydrolyzed vegetable protein. Also known as HVP, this is a protein obtained from any vegetable, including soybeans. It is used to enhance the flavor of certain foods, and is found in:
    • Soups
    • Broth
    • Sauces
    • Gravies
    • Flavorings
    • Spice blends
    • Canned/frozen vegetables
    • Meats and poultry
  • Lecithin. An ingredient extracted from soybean oil and used to promote stabilization, antioxidation, crystallization and spattering control (reducing splashing) in foods high in fat and oils. It is also used as an emulsifier (which promotes suspension of small globules of one liquid in a second liquid) in some chocolate. Many infant formulas also contain the ingredient.
  • Miso. A salty condiment derived from soybeans and grains, such as rice. It is used to flavor soups, sauces, dressings, marinades and patés.
  • Mono-diglyceride. A soy derivative used for emulsion in foods.
  • Monosodium glutamate (MSG). A food flavoring that may contain hydrolyzed protein, which is often made from soy.
  • Natto. Made of fermented and cooked whole soybeans.
  • Natural flavors (listed as such on ingredient labels). May contain a soy derivative.
  • Some fruit (canned, frozen or fresh) and fruit juices.
  • Soy cheese. Made of soy milk and often used as a substitute for sour cream or cream cheese.
  • Soy fiber. Used as food ingredients. The three basic types are:
    • Okara
    • Soy bran
    • Soy isolate fiber
  • Soy flour. Made from finely ground roasted soybeans and often used to boost protein content in recipes.
  • Soy grits. Toasted, coarsely cracked soybeans used in soy grits. These are often used as a flour substitute.
  • Soy meal/soy oil. Used in industrial products such as inks, soaps and cosmetics.
  • Soy milk. Used as an alternative to cow’s milk, or in foods such as soy yogurt, soy cheese or tofu.
  • Soy nuts. Can be in the form of nuts or added to spices such as salt or paprika.
  • Soy oil. Naturally extracted from soybeans, and found in many margarines, vegetable shortenings and pasta sauces. It also is found in Worcestershire sauce, salad dressings, mayonnaise, canned tuna, dry lemonade mix and hot chocolate mix. Soy oil is used in many types of breads, rolls, cakes, cookies and crackers and some prepackaged cereals.
  • Soy protein (sometimes labeled as soy protein concentrate, isolated soy protein, textured soy protein or textured soy flour). Often used to extend the life of meats. Soup bouillons usually contain some form of soy protein, as do meat alternatives such as tofu.
  • Soy sauces. Dark brown liquids made from soybeans that have fermented. There are three major types:
    • Shoyu (blend of soybeans and wheat)
    • Tamari (byproduct of miso)
    • Teriyaki (contains a blend of sugar, vinegar and spices)
  • Soy sprouts. Sprouted whole soybeans.
  • Soy yogurt.
  • Soybean granules or curds.
  • Tempeh. A chunky, tender soybean cake that is a traditional Indonesian food.
  • Tofu. A soft, cheese-like food made by curdling fresh hot soy milk with a coagulant. Also known as soybean curd, it has a bland taste that absorbs the flavors of other ingredients when used in cooking. People often use tofu as a meat substitute.
  • Vegetable oil. Usually 100 percent soy oil or a blend of soy oil and other oils.
  • Vitamin E supplements. May contain soybean oil.

Signs and symptoms of soy allergies

Soy allergies can produce a host of symptoms, which range from the mildly irritating to more serious reactions. Signs and symptoms of soy allergy include:

  • Acne or eczema
  • Angioedema (tissue swelling beneath the skin)
  • Rhinitis, including allergic rhinitis
  • Itching
  • Nasal congestion
  • Anaphylaxis
  • Asthma
  • Atopic dermatitis
  • Bronchospasm
  • Canker sores (open sores in mouth)
  • Colitis (inflammation of the large intestine)
  • Conjunctivitis
  • Diarrhea
  • Shortness of breath
  • Enterocolitis (inflammation of small intestine and colon)
  • Fever
  • Hypotension (low blood pressure)
  • Itching
  • Laryngeal edema (swelling of the tissues in the larynx, or voice box)
  • Hives
  • Nausea and vomiting
  • Wheezing

Diagnosis, treatment and prevention

In diagnosing a soy allergy, a physician will conduct a medical examination of the patient as well as compiling a medical history and a list of symptoms. If an allergy is suspected, the physician will perform one or more allergy tests.

The only form of treatment for soy allergy is the complete removal of problem foods from the diet, known as avoidance. There are no drugs available that can prevent a soy allergy from taking place in people who are sensitive.

Once a physician has pinpointed soy as a problem allergen, patients should remove all soy and soy-based products from their diet by paying close attention to the ingredients in the foods they eat. By checking the ingredient labels on foods at the grocery store and asking about ingredients and preparation techniques at restaurants, people can successfully avoid problem foods and control their soy allergy.

To be sure that soy is not consumed accidentally, people should also learn alternate names for soy and check the labels of processed foods for soy products.

New legislation may make it easier for people to determine if a food item contains a potential allergen. As of January 2006, food manufacturers are required by the Food & Drug Administration (FDA) to clearly list food allergens on their product labels.

Various drugs can help treat symptoms related to soy allergy reactions once they have appeared. These include antihistamines, corticosteroids, mast cell stabilizers and epinephrine. 

For a long time soy milk was considered a good alternative for infants who could not drink regular milk or were at increased risk of food allergies. However, as more and more infants switched to soy milk formulas, it became clear that soy, too, was a major food allergen (though there is no cross-reactivity between cow’s milk and soy – each triggers an allergic reaction independently). For this reason, soy formulas are no longer considered a safer type of formula for at-risk infants.

Research into creating varieties of allergen-free soybeans has yielded some success. Allergen-free soybeans have been created in laboratory tests and could one day begin to replace the allergy-causing lines currently being grown. If widely adopted, these new soybeans could reduce the number of allergies triggered by the accidental ingestion of a soy-containing food.

Questions for your doctor about soy allergies

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following soy allergy–related questions:

  1. What tests will you use to determine if I am allergic to soy?
  2. What treatment options are available to me?
  3. If I have a soy allergy, will I ever be able to eat soy products again?
  4. What products commonly contain soy?
  5. What should I do if I accidentally consume soy?
  6. Should I carry an allergy kit with me at all times?
  7. Can I still eat out at restaurants?
  8. Can I pass my soy allergy on to my children?
  9. What terms should I look for when reading product labels?
  10. Will my child outgrow his or her soy allergy?
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