Soy allergy

Symptoms

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 an hour after eating soy-containing food.

Soy allergy symptoms can include:

• Tingling in the mouth
• Hives, itching or eczema
• Swelling of the lips, face, tongue and throat, or other parts of the body
• Wheezing, runny nose or trouble breathing
• Abdominal pain, diarrhea, nausea or vomiting
• Dizziness, lightheadedness or fainting

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:

• Constriction of airways, including a swollen throat or a lump in your throat, that makes it difficult to breathe
• Shock, with a severe drop in blood pressure
• Rapid pulse
• Dizziness, lightheadedness or loss of consciousness

Soy allergy in infants often begins with the introduction of a soy-based formula. In many cases, soy allergy develops when a child is switched to a soy-based formula after an allergic reaction to a milk-based formula.

Causes

All food allergies are caused by an immune system malfunction. Your immune system identifies certain soy proteins as harmful, triggering the production of immunoglobulin E (IgE) antibodies to neutralize 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, labored breathing, and even anaphylactic shock.

Researchers have identified at least 15 possible allergens in soy protein, which comes from soybeans. Exactly how soy protein causes an allergic reaction is still not clear.

Risk factors

Certain factors may put you at greater risk of developing a soy allergy:

• Family history. You're at increased risk of allergy to soy or other foods if allergies, such as hay fever, asthma, hives or eczema, are common in your family.
• Age. Soy allergy is most common in children, especially toddlers and infants. As you grow older, your digestive system matures and your body is less likely to absorb food or food components that trigger allergies.
• 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

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:

• Skin test. In this test, your skin is pricked and exposed to small amounts of the proteins found in soy. If you're allergic, you develop a raised bump (hive) at the test location on your skin. Allergy specialists usually are best equipped to perform and interpret allergy skin tests.

• Blood test.A blood test can measure your immune system's response to soy by measuring the amount of certain antibodies in your bloodstream, known as immunoglobulin E (IgE) antibodies. A blood sample is sent to a medical laboratory, where it can be tested for evidence of sensitivity to soy.

References

http://www.mayoclinic.org/diseases-conditions/soy-allergy/basics/definition/con-20031370

http://www.healthline.com/health/allergies/soy

http://www.webmd.com/allergies/guide/soy-allergy

http://my.clevelandclinic.org/health/diseases_conditions/hic_Allergy_Overview/hic_Food_Allergies/hic_Soy_Allergy