Soy, a product of soybeans, is a common food that can cause allergies. In many cases, soy allergy starts with a reaction to a soy-based infant formula. Although most children eventually outgrow a soy allergy, soy allergy may persist into adulthood.
Often, signs and symptoms of soy allergy are mild, such as hives or itching in the mouth. In rare cases, soy allergy can cause a life-threatening allergic reaction (anaphylaxis).
If you or your child has a reaction to soy, let your doctor know. Tests can help confirm a soy allergy. If you have a soy allergy, you'll need to avoid products that contain soy. This can be difficult, however, as soy is common in many foods, such as meat products, bakery goods, chocolate and breakfast cereals.
For most people, soy allergy is uncomfortable but not serious. Rarely, an allergic reaction to soy can be frightening and even life-threatening. Signs and symptoms of a food allergy usually develop within a few minutes to hours after eating a food containing soy.
Soy allergy symptoms can include:
A severe allergic reaction to soy — called anaphylaxis — is rare. It's more likely to occur in people who have asthma or are also allergic to other foods such as peanuts. Anaphylaxis causes more extreme signs and symptoms including:
Soy allergy in infants often begins with the introduction of a soy-based formula. Soy allergy may develop when a child is switched to a soy-based formula after an allergic reaction to a milk-based formula.
When to see a doctor
Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as:
All food allergies are caused by an immune system reaction. Your immune system identifies certain soy proteins as harmful, triggering the production of immunoglobulin E (IgE) antibodies to the soy protein (allergen). The next time you come in contact with soy, these IgE antibodies recognize it and signal your immune system to release histamine and other chemicals into your bloodstream.
Histamine and other body chemicals cause a range of allergic signs and symptoms. Histamine is partly responsible for most allergic responses, including runny nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, difficulty breathing, and even anaphylactic shock.
Certain factors may put you at greater risk of developing a soy allergy:
Preparing for your appointment
Call 911 or emergency medical help, or go to an emergency room if you or your child develops symptoms of anaphylaxis, such as difficulty breathing or a rapid, weak pulse.
If symptoms of an allergic response are less severe, call your family doctor or pediatrician for an appointment. In some cases, you may be referred to a doctor who specializes in the diagnosis and treatment of allergic illness (allergist).
Here's some information to help you get ready, and what to expect from your doctor.
What you can do
If your child is the one with symptoms, also ask your doctor these additional questions:
What to expect from your doctor
If your baby or child is the one with symptoms, your doctor also may ask these additional questions:
What you can do in the meantime
If you have symptoms of soy allergy, avoid food products that contain soy until you've been evaluated by your doctor.
Tests and diagnosis
Your doctor will ask about your symptoms and may perform a physical exam to find or rule out other medical problems. He or she may also recommend one or both of the following tests:
Treatments and drugs
The only way to prevent an allergic reaction is to avoid soy and soy proteins.
Medications, such as antihistamines, may reduce signs and symptoms of soy allergies. These drugs can be taken after exposure to soy to control your reaction and help relieve discomfort. Some over-the-counter antihistamines are: diphenhydramine (Benadryl, others), chlorpheniramine (Chlor-Trimeton, others), cetirizine (Zyrtec, others) and loratadine (Alavert, Claritin, others).
Despite your best efforts, you may still come into contact with soy. If you have a serious allergic reaction, you may need an emergency injection of epinephrine and a trip to the emergency room. If you're at risk of having a severe reaction, you may need to carry injectable epinephrine (such as an EpiPen or EpiPen Jr) with you at all times. Ask your doctor for guidance, so that you're certain you know when and how to use portable epinephrine.
Lifestyle and home remedies
If you have experienced a severe allergic reaction to soy, be sure to carry injectable epinephrine (EpiPen, EpiPen Jr) with you all the time. It's also a good idea to wear a medic alert bracelet to let others know about your allergy.
There is no sure way to prevent a food allergy from occurring. But if you have an infant, breast-feeding instead of using a soy-based or milk-based formula may help. Breastfeed for at least the first four months to reduce the risk of food allergies and for other health benefits.
If you know you're allergic to soy, the only sure way to avoid an allergic reaction is to avoid soy products. It's not always easy to know which foods contain soy, however, and it's a commonly used ingredient in many foods.
Try to learn as much as you can about what you're eating and drinking. Be sure to read food labels carefully. Because soybeans and peanuts contain common allergy-causing components, you may also need to avoid peanuts as well. Some processed soy foods, such as soy oil or soy sauce, may not cause a reaction because processing removes certain allergy-causing proteins.
Soy milk, edamame, tofu and other soy products have become more popular because of their apparent health benefits. Soy may be called any of the following on a product label:
But soy is also a common ingredient in other food products, and it's not always easy to know if a product contains soy. It's used in meat products and meat substitutes, baked goods, candies, ice creams and desserts, condiments, butter substitutes, and in other foods.
Products with soy as a main ingredient
Hidden sources of soy products
Also, check for the statement "contains soy" on the product label.
Last Updated: 2011-05-20
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