What is a soy allergy?

Soy is one of the most common causes of IgE-mediated food allergies in infants and young children.  In most cases, soy allergies develop and are diagnosed in early childhood

Soy is a legume like peas, peanuts, lentils and beans. It is a common ingredient in some infant formula and processed foods.

Causes of soy allergies

Soy allergies occur when the immune system misidentifies soy proteins as being harmful. The body releases histamine to protect itself. Histamine causes symptoms such as coughing, wheezing and hives.

Signs and symptoms of a soy allergy

If your child is allergic to the protein, it may cause symptoms in multiple areas of the body, including:

• Skin: hives (red, blotchy skin that can itch) and may include mild to severe swelling
• Lungs: difficulty breathing, shortness of breath, coughing or wheezing
• Eyes: itching, tearing or redness
• Throat: tightness, trouble breathing or inhaling
• Stomach: repeated vomiting, nausea, abdominal pain and cramping or diarrhea
• Nose: congestion, copious clear discharge, sneezing or itching
• Neurologic: change in behavior or mood, dizziness
• Drop in Blood Pressure: This is the most dangerous symptom of a severe allergic reaction

If your child experiences any of these symptoms after ingesting soy, call your pediatrician and arrange to have your child tested by a pediatric allergist.

If a child has any two systems involved from the above list, this means they may be experiencing anaphylaxis.

If your child has symptoms of anaphylaxis, call 911 immediately.

Testing and diagnosis of soy allergies

If you suspect your child is allergic to soy, clinicians at Children’s Hospital of Philadelphia will take a detailed medical history of your child, including information on any prior food reactions. Based on your child’s history and findings, our clinicians may order one or more of the following tests:

Skin test

In allergy skin testing, a very small amount of the soy is introduced to the skin — typically on your child’s forearm — through a gentle pinprick. The appearance of a hive-like red bump may indicate a soy milk allergy.

Blood test

In allergen-specific IgE blood tests, a small amount of your child's blood is drawn and tested for antibodies the child may have produced in response to exposure to soy.

Food challenge

A food challenge test involves giving your child a small increasing amounts of soy in a controlled, highly supervised clinical setting to monitor for any reactions. 

Treatments for soy allergies

The first step in treating a soy allergy is to avoid foods that contain soy. Soy is used in many foods so it’s important to carefully read food labels.

U.S. manufacturers are required to clearly label foods containing common allergens, including soy. Your child’s doctor can give you detailed information on how to read food labels to help identify and avoid soy.

No matter how careful you are, there may be times your child accidentally ingests soy and has an allergic reaction. If that happens, you can treat the symptoms with antihistamines or epinephrine.

If more than one body system is involved – for example throat and stomach – it is recommended to use epinephrine. Epinephrine comes in a variety of forms, including auto-injectors such as Epi-Pen, Auvi-Q and other generic forms.

If your child’s reaction is mild and only involves a few hives, an over-the-counter or prescription strength antihistamine can ease the symptoms. Your child’s doctor can help you decide which option is best for your child in each circumstance.

Children with soy food allergies should always carry epinephrine with them, or it should be readily available at places where they routinely spend time, such as school, daycare and home.

When to call 911

If your child has a severe reaction or signs of anaphylaxis, administer epinephrine and then call 911 right away. In some circumstances, children may need more than one dose of epinephrine, so it is important to have medical assistance in these situations if needed.

Oral immunotherapy

Oral immunotherapy (OIT), may help desensitize your child to soy. Your child will ingest small quantities of soy protein in a controlled setting to monitor for reactions, then continue that amount of soy protein every day at home. The amount of soy protein will be gradually increased under close medical supervision at the hospital. Your healthcare provider can help you determine if oral immunotherapy may be appropriate for your child. If so, you'll receive a referral to CHOP’s Oral Immunotherapy Program.

Follow-up care for soy allergies

Your child’s healthcare provider will give you and your family more information on how to avoid exposure to soy and treat any reactions your child may experience.

You may also want to share information about your child's soy allergy with your extended family, close friends and your child’s school know so they can help reduce the chance of accidental exposure to the allergen outside your home.

Some children with food allergies, including to soy will eventually outgrow the. It's important that your child undergo a supervised test – such as a food challenge – to determine if they must continue avoiding the food or can incorporate it into their diet.

Outlook for children with soy allergies

Many children outgrow their allergy to soy during childhood. Your child should undergo a supervised test, such as a food challenge to determine whether it’s safe to incorporate soy into their diet.