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Soy Allergy

What is a soy allergy?

A soy allergy is a reaction by your child's immune system to the protein in soybeans. Our immune systems normally respond to bacteria or viruses that attack the body. A food allergy occurs when the body's immune system mistakenly believes that a harmless substance (such as proteins found in soy) is harmful. In order to protect the body, the immune system creates substances called antibodies to that food. The next time you eat that particular food, your immune system releases huge amounts of chemicals, such as histamines, to protect the body. This is what causes the warning symptoms.

Soy is one of the 8 foods that are responsible for most food allergies in children. The other foods include eggs, cow's milk, peanuts, tree nuts (such as walnuts and cashews), wheat, fish, and shellfish.

Soybeans are in the legume family (kidney beans, lentils, peas, and peanuts). Some people are allergic to more than one type of legume. A soy allergy is most common in infants and is usually noticed by 3 months of age. Most children outgrow this allergy by 3 years of age.

What are the symptoms of an allergic reaction to soy?

Usually symptoms start within a few minutes to an hour after eating a food that contains soy. If you think your child is allergic to soybeans, soy products or any other food, it is important to get a diagnosis from your healthcare provider or allergist. You should look for the following symptoms, which can range from mild to severe:

  • skin reactions such as hives, eczema, acne
  • diarrhea, nausea, vomiting, stomach pain, or itching around the mouth
  • running nose, wheezing or trouble breathing
  • swelling and itching
  • fever blisters
  • asthma
  • fever, weakness
  • pink eye (conjunctivitis)

Although rare, it is possible to have an allergic reaction called anaphylactic shock. This is a serious reaction that is sudden, severe, and can involve the whole body. It can cause swelling of the mouth and throat, dangerously lower blood pressure, and trouble breathing. This type of reaction is a medical emergency. It is treated with epinephrine (a medicine that is given by injection). Usually parents or caregivers of children who have severe allergic reactions carry their own shot kits, just in case of emergency.

An allergic reaction to a food usually starts within minutes but may be delayed 2 to 4 hours. It usually lasts less than 1 day. The more severe the allergy, the smaller the amount of food it takes to cause a reaction.

What kind of formula should I use?

If your child is only allergic to soy, you can use regular (non-soy) baby formula. However, about half of the children with a slow-onset milk allergy are also allergic to soy. In these cases, you will need to switch to a hypoallergenic formula. There are two types of hypoallergenic formulas.

  • Extensively hydrolyzed formulas: The proteins in these formulas have been broken down so that they are more easily digested and less likely to cause a reaction. Brands include Nutramigen LIPIL with Enflora, Pregestimil, and Alimentum. Partially hydrolyzed formulas are not a good substitute.
  • Elemental formulas: The proteins in these formulas are in the simplest form and are used when hydrolyzed formula continues to cause symptoms. Elemental formulas include Neocate, Elecare and Nutramigen AA LIPIL.

How will this affect my child's diet?

The only treatment for a child with a soy allergy is to completely avoid soy and foods that contain soy products. Many foods contain soy, such as baked goods, cereals, sauces, soups and even canned tuna. You will need to change the way you shop and prepare foods. Eliminating all the products in which soy products are found may lead to vitamin deficiency. It is a good idea to have a pediatric dietitian check your child's diet from time to time. Most children with soy allergy can have soybean oil that is not cold pressed, expeller pressed or extruded. Ask your healthcare provider if your child needs to avoid soybean oil.

The first step is to learn to read labels and become familiar with ingredients that contain soy or soy products are present. Avoiding soy can be difficult as soybeans are used in most processed foods found in this country. Ask about the ingredients in foods prepared in restaurants when you eat out.

Foods and ingredients that contain soy

  • Edamame (soybeans)
  • Soya
  • Soy Milk
  • Soy protein
  • Soy sauce
  • Worcestershire sauce
  • Soybean (granules, curd)
  • Soy (flour, fiber, albumin, grits, nuts, fruits, sprouts)
  • Soy protein as hydrolyzed, concentrate, isolate
  • Tofu (soybean curd)
  • Tamari
  • Tempeh
  • Miso

Foods that often contain soy (check label or ask)

  • Most Asian Foods (both packaged and served in restaurants)
  • Flavoring (natural or artificial)
  • Vegetable starch
  • Vegetable broth or gum
  • Vegetable oil
  • Textured vegetable protein (TVP)
  • Hydrolyzed plant protein
  • Lecithin
  • Monosodium glutamate (MSG)
  • Vitamin E
  • Some brands of peanut butter
  • Cereals
  • Baked goods
  • Some infant formulas

Reading labels to avoid allergens has become a lot easier. Foods that contain milk, eggs, fish, shellfish, peanuts, tree nuts, wheat, or soy products must list the food in plain language on the ingredient list. For example, tempeh (soy). These possible allergens must be listed even if they are part of a flavoring, coloring, or spice blend. There are still some things to watch out for when reading food labels:

  • Read the label every time. The manufacturer may change ingredients.
  • Watch out for the words "may contain". Milk, peanuts, or other allergens may not be ingredients, but the food may be made in a factory that also produces these foods. If you see the words "may contain", there may be very little of the allergen, or there may be a large amount.
  • Words on the package such as "peanut free" or "milk free" do NOT mean that the food is completely without these allergens. You still need to read the label carefully to make sure that it does not contain ingredients derived from allergens.

It is very important for you to know less common names and scientific names for food ingredients.

Research shows that most people with a soy allergy may safely eat soy lecithin and refined soybean oil. Ask your healthcare provider if it is OK for your child to have these foods.

How can I provide my child with a healthy diet that tastes good?

Your child can still have a nutritionally complete diet as well as continue to enjoy some kid favorites. The primary nutrients found in soy are protein, calcium, fiber, B vitamins and iron. It is not difficult to provide your child with a nutritious diet, using healthy unprocessed foods from all the food groups. You may need to prepare desserts, such as cookies and cakes from scratch or buy specialty products from the health food section of your grocery store or health food store. There are also Web sites where you can buy specialty foods online (such as To be on the safe side, buy products that have an 800 number for you to call and ask about ingredients.

It is also helpful to get cookbooks for people with food allergies, such as The NEW-Food Allergy and Anaphylaxis Network (FAAN) Cookbook - Cooking Allergy-Free Everyday. Visit the Web site at or call 800-929-4040 to order this cookbook and others.

How can I keep my child safe at school?

  • Teach your child not to eat foods unless they are safe. Even young children can grasp this concept, especially once they have gotten sick after eating a particular food.
  • Prepare your child's lunch at home.
  • Talk with teachers and the school administrator about your child's needs. Ask teachers to keep an eye out and explain the situation to other children if needed.
  • Have the teacher call you if there is a special event or party planned so that you can bring a few modified treats that your child enjoys and can share with other kids.
  • Make a card that lists foods and ingredients that should be avoided and give one to the teacher. The card can also be helpful to older children in making decisions when out with friends.
Written by Terri Murphy, RD, CDE for RelayHealth.
Published by RelayHealth.
Last modified: 2010-01-27
Last reviewed: 2010-01-11
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
2010 RelayHealth and/or its affiliates. All Rights Reserved.
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