What is a Soy Allergy?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 17 January 2019
  • Copyright Protected:
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A soy allergy is a very common food allergy which develops in response to exposure to certain proteins found in soy beans. Infants and children are most prone to developing soy allergies, and they often outgrow them by age five, but the allergy can persist into adulthood. The severity of a soy allergy can vary considerably, from mild discomfort experienced after eating soy products to more serious complications like anaphylactic shock and death.

Like other food allergies, a soy allergy develops when the body's immune system identifies soy as harmful, developing antibodies to certain proteins found in soy beans. When the body is exposed to these proteins, a cascading reaction starts as the immune system tries to neutralize the invader and goes haywire. This reaction causes a number of symptoms.

Some symptoms of soy allergy include an itchy or tingling sensation in or around the mouth after eating soy, along with intestinal discomfort after eating soy. Some people develop dermatitis, or more serious symptoms like hives. In rare cases, the soy allergy can be so severe that the bronchial passages close up when someone eats soy, causing him or her to go into anaphylactic shock, a life threatening condition. This is more common in patients with preexisting lung conditions like asthma.


Someone who is allergic to soy may also be allergic to other legumes like lentils and peanuts. When a patient is diagnosed with a soy allergy, it is a good idea to discuss other potential allergens with a doctor. The doctor may recommend allergy testing to determine if the patient has other allergies, so that these foods can be avoided. Because some people can grow out of allergies, including allergies to soy, a doctor might also suggest reintroducing soy products at some point in the future, usually in small amounts and in a controlled setting.

Avoiding soy ingredients is a big challenge, because soy is used in a lot of foods. Obvious sources of soy include soy sauce, tofu, tempeh, natto, edamame, and soymilk. Soy is also used to add protein to many vegetarian foods, and to bulk out other foods. Foods with ingredients like “vegetable protein” often contain soy, and soy products such as soy oil and soy lecithin are also commonly used in prepared foods. One of the best ways to avoid soy is to avoid packaged foods altogether, preparing foods from basic ingredients to confirm that no soy is present.



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