Soy is a common cause of food allergy. Soy comes from soybeans, which are in the legume family (along with beans, lentils, peas, and peanuts). Some people are allergic to just one type of legume; others are allergic to more than one.
When someone is allergic to soy, the body's immune system, which normally fights infections, overreacts to proteins in soy. If the person eats something made with soy, the body thinks these proteins are harmful invaders and responds by working very hard to fight off the invader. This causes an allergic reaction.
Allergy to soy is more common in infants and kids than teens and adults, but can develop at any age.
What Are the Signs & Symptoms of a Soy Allergy?
When someone with a soy allergy has something with soy in it, the body releases chemicals like . This can cause symptoms such as:
a drop in blood pressure, causing lightheadedness or loss of consciousness (passing out)
Allergic reactions to soy can differ. Sometimes the same person can react differently at different times. Most reactions to soy are mild and involve only one system of the body, like hives on the skin. Other times the reaction can be more severe and involve more than one part of the body.
Rarely, soy allergy can cause a severe reaction called anaphylaxis. Anaphylaxis might start with some of the same symptoms as a less severe reaction, but can quickly get worse. The person may have trouble breathing or pass out. More than one part of the body might be involved. If it isn't treated, anaphylaxis can be life-threatening.
How Is an Allergic Reaction to Soy Treated?
If your child has a soy allergy (or any kind of serious food allergy), the doctor will want him or her to carry an epinephrine auto-injector in case of an emergency.
An epinephrine auto-injector is a prescription medicine that comes in a small, easy-to-carry container. It's easy to use. Your doctor will show you how. Kids who are old enough can be taught how to give themselves the injection. If they carry the epinephrine, it should be nearby, not left in a locker or in the nurse's office.
Wherever your child is, caregivers should always know where the epinephrine is, have easy access to it, and know how to give the shot. Staff at your child's school should know about the allergy and have an action plan in place. Your child's medicines should be accessible at all times.
Every second counts in an allergic reaction. If your child starts having serious allergic symptoms, like swelling of the mouth or throat or difficulty breathing, give the epinephrine auto-injector right away. Also give it right away if the symptoms involve two different parts of the body, like hives with vomiting. Then call 911 and take your child to the emergency room. Your child needs to be under medical supervision because even if the worst seems to have passed, a second wave of serious symptoms can happen.
It's also a good idea to carry an over-the-counter (OTC) antihistamine for your child, as this can help treat mild allergy symptoms. Use after — not as a replacement for — the epinephrine shot during life-threatening reactions.
What Else Should I Know?
If allergy testing shows that your child has a soy allergy, the doctor will give you guidelines on keeping your child safe. Your child may need to completely avoid products made with soy. This can be tough as soy has become part of many foods. For information on foods to avoid, check sites such as the Food Allergy Research and Education network (FARE).
Always read food labels to see if a food contains soy. Manufacturers of foods sold in the United States must state whether foods contain any of the top eight most common allergens, including soy. The label should list "soy" in the ingredient list or say "Contains soy" after the list.
Some foods look OK from the ingredient list, but while being made they can come in contact with soy. This is called cross-contamination. Look for advisory statements such as "May contain soy," "Processed in a facility that also processes soy," or "Manufactured on equipment also used for soy." Not all companies label for cross-contamination, so if in doubt, call or email the company to be sure.
When eating away from home, make sure you have an epinephrine auto-injector with you and that it hasn't expired. Also, tell the people preparing or serving your child's food about the soy allergy. Sometimes, you may want to bring food with you that you know is safe. Don't eat at the restaurant if the chef, manager, or owner seems uncomfortable with your request for a safe meal.
Also talk to the staff at school about cross-contamination risks for foods in the cafeteria. It may be best to pack lunches at home so you can control what's in them.
Other things to keep in mind:
Make sure the epinephrine auto-injector is always on hand and that it is not expired.
Don't feed your child cooked foods you didn't make yourself or anything with unknown ingredients.
Tell everyone who handles the food — from relatives to restaurant staff — that your child has a soy allergy.