Soy Allergy: Avoiding Soy-Based Food Products
Soy allergy is an adverse reaction to foods, beverages and other products derived from soybeans. It can provoke a host of symptoms, ranging from nasal congestion or diarrhea to potentially serious manifestations such as bronchospasm or anaphylaxis (a dangerous allergic reaction which involves two or more body systems). Soy is an allergen for many children but only a few adults. Soy allergy often appears in the first three months of life and disappears by the time a child is two years old.
Soybeans are legumes native to East Asia that can be found in many processed food products, including soy milk, tofu and vegetable oils, as well as in furniture, soaps and cosmetics. Because soy is present in so many different products, patients with soy allergy must become familiar with these products to steer clear of them. Complete avoidance is the only technique certain to prevent symptoms.
Since soy is a major food allergen, soy infant formula, once a popular alternative to cow’s milk formula, is no longer considered a safer option for at-risk infants.
Potential Causes of Soy Allergy
Soy can be consumed in plant form as a pod or seed or as a substance added to processed food products, such as cheese, meat substitutes or soups. Soy is also a source of edible oil and can be found in many vegetable oils. In addition, soy is commonly used in a variety of non-food products like soaps, cosmetics or coatings. In sensitive individuals, contact with these non-food products will result in an allergic skin reaction called atopic dermatitis. Individuals with soy allergies may also experience cross-reactions to other legumes (plants of the same species), including:
- Black beans
- Chick peas
- Green peas
- Kidney beans
- Lima beans
- Navy beans
- Pinto beans
- String beans
Moreover, many ingredients in common foods contain some type of soy product, including:
- Fruits. Canned or frozen fruit and fruit juices may contain a soy derivative.
- Hydrolyzed vegetable protein (HVP). This is a protein derived from any vegetable, including soybeans. HVP is used to enhance the flavor of many foods. It can be found in broth, canned and/or frozen vegetables, flavorings, gravies, meats and poultry, sauces, soups and spice blends.
- Lecithin. This is a fatty substance extracted from soybean oil used as a stabilizer, antioxidant and emulsifier in foods high in fat and oils and as a surfactant in industrial paint applications. It can be also found in chocolate and soy infant formulas.
- Miso. A salty seasoning made of fermented soybeans and rice used to flavor dressings, marinades, patés, sauces and soups.
- Mono-diglyceride. A soy derivative used as an emulsifier in foods.
- Monosodium glutamate (MSG). A food flavoring that may contain hydrolyzed vegetable protein mentioned above, which is often made from soy.
- Natto. Made of fermented and cooked whole soybeans.
- Natural flavors. May also contain a soy derivative.
- Soybean granules or curds.
- Soy cheese. Made of soy milk.
- Soy fiber. Food ingredients including okara, soy bran and soy isolate fiber.
- Soy flour. Made from finely ground roasted soybeans.
- Soy grits. Coarsely cracked, toasted soybeans often used as a flour substitute.
- Soy meal. Used in industrial products like cosmetics, soaps and inks.
- Soy milk. An alternative to cow’s milk, but can be also used in foods such as soy cheese, tofu or soy yogurt.
- Soy nuts. Can be added to spices.
- Soy oil. Extracted from soybeans and present in mayonnaise, salad dressings, vegetable shortenings, margarines, canned tuna, pasta sauces, Worcestershire sauce, hot chocolate mix and dry lemonade mix. Soy oil is also found in cakes, cookies, crackers, breads, rolls and some cereals. In addition, soy oil finds many uses in industry (e.g., coatings, paints, plasticizers for polyurethane foam).
- Soy protein (sometimes also labeled as isolated soy protein, soy protein concentrate, textured soy protein or textured soy flour). Often used to extend the shelf-life of meats. Soup bouillons and meat alternatives usually contain some form of soy protein.
- Soy sauces. Dark brown liquids made from fermented soybeans, including shoyu (blend of soybeans and wheat), tamari (byproduct of miso) and teriyaki (contains a blend of vinegar, sugar and spices). Other sauces (e.g., Worcestershire sauce) may also contain soy.
- Soy sprouts. Sprouted whole soybeans.
- Soy yogurt.
- Tempeh. A chunky, tender soybean cake that is a traditional Indonesian dish.
- Tofu. Also known as soybean curd often used as a meat substitute. Tofu is a soft, cheese-like food that has a bland taste and easily absorbs the flavors of other ingredients when used in cooking.
- Vegetable oil. Often 100% soy oil or a blend of soy oil and other vegetable oils.
- Vitamin E supplements. May also contain soybean oil.
Symptoms of Soy Allergies
Like most other allergies, soy allergies can produce a wide range of symptoms, which range from the mildly irritating to more serious reactions, including:
- Atopic dermatitis
- Canker sores
- Laryngeal edema
- Nasal congestion
- Nausea and vomiting
- Rhinitis, including allergic rhinitis
- Shortness of breath
Diagnosing Soy Allergy
Soy allergies are diagnosed in a similar way to most other food allergies. For more details on tests used to identify a soy allergy read this post about milk allergy (these tests are identical for both allergies).
Treatment and Prevention of Soy Allergy
Although there is no cure for soy allergy and no drugs can prevent it from taking place in sensitive people, it can be easily managed by removing problem foods from the diet.
Patients must avoid all soy-based products by paying close attention to the ingredients in the foods they eat. They should also learn alternate names for soy and soy ingredients (see the section “Potential Causes of Soy Allergy” above) and check the labels of processed foods for soy products. All allergens must be clearly listed on the product labels as required by the FDA.
Certain drugs can be prescribed to alleviate symptoms related to soy allergy. They include antihistamines, bronchodilators (incl. epinephrine injections), corticosteroids and mast cell stabilizers. However, they should only be used to treat symptoms once they have appeared and not to prevent them from occurring.