What Is a Soy Allergy?
A soy allergy is when your body reacts to soy protein. Soy protein is a product of soybeans and it’s in many foods. If you are allergic to soy, your immune system will react anytime you come in contact with it.
Soy Allergy Symptoms
Symptoms usually happen within minutes or hours. They may include:
- Hives or itching
- Swelling of lips, mouth, or other body parts
- Belly pain, nausea, or vomiting
- Red skin
If you have more serious allergy symptoms, you may have a severe reaction called anaphylaxis. It needs immediate care. Signs of anaphylaxis include:
- Trouble breathing
- Shock and a severe drop in blood pressure
- Rapid heart rate
- Dizziness, lightheadedness, or blacking out
If you or someone you know has signs of anaphylaxis, call 911. It’s a medical emergency.
Soy Allergy Causes and Risk Factors
Allergies happen when your immune system overreacts to something. If you have a soy allergy, soy proteins trigger your immune system to react. This will happen anytime your immune system is exposed to this protein.
Part of this reaction is a release of chemicals including histamines. These chemicals cause your symptoms.
Some things make soy allergy more likely. They include:
- Family history of allergy to soy or other foods
- Young age
- Allergies to other foods such as wheat, beans, or milk
Soy Allergy Diagnosis
If you think you have a soy allergy, your doctor can test for it. They may recommend these tests:
- Skin test. Your doctors will prick your skin with a needle that has a small amount of soy protein. If you are allergic, your skin will make a bump in that spot.
- Blood test. Your doctor can draw blood to measure your immune response to soy protein.
Soy Allergy Prevention
If you have a soy allergy, you need to do more than skip soy sauce and tofu. Soybeans are a big part of processed foods, too.
Do these things to protect yourself or your child from an allergic reaction:
- Always read labels. In the U.S., "soy" must be listed on the label if it’s in a food.
- Be careful at restaurants. Even if you order a soy-free dish, you could still be exposed because the ingredient is used so often in foods from Asian cultures. A cook might use the same utensil on soy and non-soy dishes. Explain that you need to be sure your food doesn’t touch soy in any way.
- Ask your doctor about soy oil and lecithin. Most people with soy allergies can handle highly refined soy oil. The same goes for soy lecithin, which is often used in chocolate candy, peanut butter, and margarine. Avoid cold-pressed, expelled, or extruded soy oil -- sometimes called gourmet oils. These ingredients are different and aren’t safe to eat if you’re allergic to soy. Your doctor or an allergist can help you figure out which are OK for you.
Soy foods to stay away from
If you have a soy allergy, do not eat these foods:
- Soy sauce and shoyu sauce
- Soy-based fiber, flour, grits, nuts, or sprouts
- Soy-based milk, yogurt, ice cream, or cheese
- Soy protein
- Teriyaki sauce
- Textured vegetable protein (TVP)
Foods that may contain soy
These foods may have soy:
- Baked goods (breads, cookies, and crackers)
- Canned broth and soup
- Canned tuna and meat
- Frozen dinners
- High-protein energy bars and snacks
- Ice cream
- Infant formula, baby foods, and cereals
- Low-fat peanut butter
- Meat substitutes
- Processed meats, like deli meats
- Salad dressings, mayonnaise, gravy, and sauces
- Vegetable oil
- Worcestershire sauce
Other names that may mean soy ingredients
You may want to skip any products with these names on their ingredient lists.
- Glycine max
- Hydrolyzed vegetable protein (HVP)
- Monosodium glutamate (MSG)
If you see an ingredient you aren’t familiar with, follow a simple rule: When in doubt, look it up. You can email the maker of the product if you're still not sure about something.