Definition

What is soy allergy?

Allergy to soy, a product of soybeans, is a common food allergy. Often, soy allergy starts in infancy with reaction to soy-based infant formula. Although most children outgrow soy allergy, some carry the allergy into adulthood.

Mild signs and symptoms of soy allergy include hives or itching in and around 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.

Having a soy allergy means avoiding products that contain soy, which can be difficult. Many foods, such as meat products, bakery goods, chocolate and breakfast cereals, may contain soy.

How common is soy allergy?

Soy allergy is common. Please discuss with your doctor for further information.

Symptoms

What are the symptoms of soy allergy?

The common symptoms of soy allergy are:

  • Tingling in the mouth
  • Hives; itching; or itchy, scaly skin (eczema)
  • Swelling of lips, face, tongue and throat, or other body parts
  • Wheezing, runny nose or breathing difficulty
  • Abdominal pain, diarrhea, nausea or vomiting
  • Skin redness (flushing)

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 the allergen.

A severe allergic reaction (anaphylaxis) is rare with a soy allergy. It’s more likely to occur in people who also have asthma or who are allergic to other foods besides soy, such as peanuts.

Anaphylaxis causes more-extreme signs and symptoms including:

  • Difficulty breathing, caused by throat swelling
  • Shock, with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness, lightheadedness or loss of consciousness

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

See your primary care doctor or a doctor who specializes in treating allergies (allergist) if you experience food allergy symptoms shortly after eating. If possible, see your doctor during an allergic reaction.

Seek emergency treatment if you develop signs or symptoms of anaphylaxis, such as:

  • Difficulty breathing
  • Rapid, weak pulse
  • Dizziness or lightheadedness
  • Drooling and inability to swallow
  • Full-body redness and warmth (flushing)

Causes

What causes soy allergy?

An immune system reaction causes food allergies. With a soy allergy, 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 anaphylactic shock.

Food protein-induced enterocolitis syndrome (FPIES)

A food allergen can also cause what’s sometimes called a delayed food allergy. Although any food can be a trigger, soy is one of the most common. The reaction, commonly vomiting and diarrhea, usually occurs within hours after eating the trigger rather than minutes.

Unlike some food allergies, FPIES usually resolves over time. As with typical soy allergies, preventing a reaction involves avoiding foods with soy.

Risk factors

What increases my risk for soy allergy?

There are many risk factors for soy allergy, such as:

  • Family history. You’re at increased risk of allergy to soy or other foods if other allergies, such as hay fever, asthma, hives or eczema, are common in your family.
  • Soy allergy is most common in children, especially toddlers and infants.
  • Other allergies. In some cases, people who are allergic to wheat, beans (legumes), milk or other foods can have an allergic reaction to soy.

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is soy allergy diagnosed?

The allergist will take a history and conduct a physical examination. You may be asked to keep a food diary, noting not just what is eaten, but what symptoms occur after food is consumed.

In addition, the allergist may recommend a skin-prick test or a blood test, both of which check for the presence of immunoglobulin E (IgE) antibodies to soy protein.

In the skin-prick test, a small amount of a liquid containing soy protein is placed on the back or forearm, which is then pricked with a small, sterile probe to allow the liquid to seep into the skin. The presence within 15 to 20 minutes of a raised, reddish spot can indicate an allergy. In the blood test, a blood sample is sent to a laboratory to test for the presence of IgE antibodies; the result is reported as a numerical value.

If these tests aren’t definitive, the allergist may order an oral food challenge. Under medical supervision, the person being tested will eat small amounts of an item containing soy to see whether symptoms develop. Because of the possibility that a reaction could be severe, this test is conducted in your allergist’s office or at a food challenge center with emergency equipment and medication on hand.

How is soy allergy treated?

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. Taking an antihistamine after exposure to soy may control your reaction and help relieve discomfort. Over-the-counter antihistamines include: diphenhydramine (Benadryl, others), chlorpheniramine (Chlor-Trimeton, others), cetirizine (Zyrtec, others) and loratadine (Alavert, Claritin, others).

Despite your best efforts, you can ingest soy unknowingly. If you have a serious allergic reaction, you may need an emergency injection of epinephrine and a trip to the emergency room.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage soy allergy?

The following lifestyles and home remedies might help you cope with soy allergy:

  • Carry injectable epinephrine (EpiPen, Auvi-Q, others) with you always. Make sure you know when and how to use portable epinephrine.
  • Wear a medical alert bracelet to let others know about your allergy.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: December 13, 2017 | Last Modified: December 13, 2017

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