Soybeans are in the legume
family, which also includes foods such as kidney beans, peas, lentils, and
peanuts. Soybeans, also called edamame, are used in a lot of processed foods in
the United States. Although primarily associated with tofu, soy is found in
many unexpected, processed foods, such as:
- condiments like Worcestershire
- natural and
- vegetable broths and
- frozen meats
- frozen meals
- most Asian foods
- certain brands of
- some peanut butters
Soy is one of
the most difficult products for allergy sufferers to avoid.
A soy allergy occurs when the
body’s immune system mistakes the harmless proteins found in soy for invaders
and creates antibodies against them. The next time a soy product is consumed,
the immune system will release chemicals such as histamines to “protect”
the body. The release of these chemicals causes an allergic reaction.
Soy, along with cow’s milk, eggs,
peanuts, tree nuts, wheat, fish, and shellfish, make up the “big eight”
allergens. These are responsible for 90 percent of all food allergies, according
to the Cleveland Clinic. Soy
allergies are one of several food allergies that begin early in life and may
resolve by age 3.
a soy allergy may range from mild to severe and include:
- abdominal pain
- diarrhea, nausea, or
- runny nose,
wheezing, or trouble breathing
- fever blisters
- conjunctivitis (pink
- skin reactions
including hives and eczema
- itching and swelling
- anaphylactic shock
(very rarely in the case of soy allergies)
symptoms in infants may include crying, irritability, and soy avoidance.
Types of Soy Allergies
Soy and soy products can trigger a variety of allergy
types. These include:
Soy Lecithin Allergy
Soy lecithin is a nontoxic food
additive. It’s used in foods that
require a natural emulsifier. Lecithin helps control sugar crystallization in
chocolates, improves shelf life in some products, and reduces spattering while
frying certain foods. Most people who are allergic to soy may tolerate soy
lecithin, according to the National Food Management Institute.
Soy Milk Allergy
Nearly half of children with a
slow-onset cow’s milk allergy are also allergic to soy. If a child is on a
formula, parents must switch to a hypoallergenic formula. In extensively
hydrolyzed formulas, proteins have been broken down so they are less likely to
cause an allergic reaction. In elemental formulas, the proteins are in the
simplest form and unlikely to cause a reaction.
Soy Sauce Allergy
In addition to soy, soy sauce
also usually contains wheat, which may make it difficult to decipher whether
allergic symptoms were caused by one allergen or the other. In addition, soy
sauce also contains histamines, according to Food and Chemical Toxicology. This may result in histamine poisoning, which causes
symptoms similar to an allergic reaction, including inflammation around the
mouth and dermatitis. A skin prick test or other test should be used to
determine which allergen — if any — was behind the symptoms.
Soybean oil typically doesn’t contain proteins and is generally safe to consume for
those with soy allergies. However, you should still discuss it with your doctor
before consuming it.
There are at least 15 proteins in
soybeans that have been found to cause allergic reactions. Check labels for all
forms of soy if you have a soy allergy. You may spot several forms of soy,
- soy flour
- soy fiber
- soy protein
- soy nuts
- soy sauce
There are several tests available
to confirm soy and other food allergies. Your doctor may use one or more of the
following if they suspect you have a soy allergy:
- Skin prick test: A
drop of the suspected allergen is put on the skin and a needle is used to prick
the top layer of skin so a tiny amount of the allergen can enter the skin. If a
person is allergic to soy, a red bump similar to a mosquito bite will appear at
the spot of the prick.
- Intradermal skin test:
This test is similar to a skin prick except a small amount of the allergen is
injected underneath the skin with a syringe. It is more
sensitive than a skin prick test and may be needed if other tests are negative.
test (RAST): Blood tests are sometimes
done on babies less than a year old because their skin doesn’t react as well to prick tests. A RAST test measures the
amount of the IgE antibody in the blood.
- Food challenge test:
A food challenge is considered to be the best way to test for food allergies. A
person is given increasing amounts of the suspected allergen while a doctor
checks for symptoms.
- Elimination diet:
With an elimination diet, a person stops eating the suspected foods for a couple of weeks and then slowly adds them back into their
diet one at a time, while recording any symptoms.
The only definitive treatment for
a soy allergy is complete avoidance of soy and soy products. People with soy
allergies and parents of children with soy allergies must read labels to
familiarize themselves with ingredients that contain soy. You should also ask
about ingredients in items served in restaurants. New research from Beneficial Microbes Journal reveals a link between probiotics, specifically
Lactobacillus, and allergy prevention and management. More research is needed in
this area to be able to provide specific recommendations.
Children who have a soy allergy may outgrow this
condition by the age of 10, according to the American College of Allergy, Asthma and Immunology. It’s important to recognize the signs of a soy
allergy and take precautions to avoid a reaction. In rare cases, a soy allergy
can cause throat swelling, a potentially life-threatening condition.