Soybeans are in the legume family, which also includes foods such as kidney beans, peas, lentils, and peanuts. Whole, immature soybeans are also known as edamame. Although primarily associated with tofu, soy is found in many unexpected, processed foods in the United States, such as:
Soy is one of the most difficult products for people with allergies 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 releases substances such as histamines to “protect” the body. The release of these substances causes an allergic reaction.
Soy is one of the “Big Eight” allergens, along with cow’s milk, eggs, peanuts, tree nuts, wheat, fish, and shellfish. These are responsible for 90 percent of all food allergies, according to the Cleveland Clinic. Soy allergy is one of several food allergies that begins early in life, usually before age 3, and often resolves by age 10.
Symptoms of a soy allergy may range from mild to severe and include:
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 University of Nebraska Food Allergy Research. This is because soy lecithin typically doesn’t contain enough of the soy protein responsible for allergic reactions.
It’s estimated that about fifteen percent of infants who are allergic to cow’s milk 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’re less likely to cause an allergic reaction. In elemental formulas, the proteins are in the simplest form and unlikely to cause a reaction.
In addition to soy, soy sauce also usually contains wheat, which may make it difficult to decipher whether allergic symptoms were caused by soy or by wheat. If wheat is the allergen, consider tamari instead of soy sauce. It’s similar to soy sauce but usually made without adding wheat products. A skin prick test or other allergy testing should be used to determine which allergen — if any — was behind any allergic symptoms.
Soybean oil typically doesn’t contain soy proteins and is generally safe to consume for those with soy allergies. However, you should still discuss it with your doctor before consuming it.
According to experts, it’s unusual for people with a soy allergy to only be allergic to soy. People with soy allergies often also have allergies to peanuts, cow’s milk, or birch pollen.
There are at least 28 possible allergy-causing proteins in soybeans that have been identified. However, most allergic reactions are only caused by a few. Check labels for all forms of soy if you have a soy allergy. You may spot several forms of soy, including:
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:
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.
Research is ongoing as to the potential role of probiotics in preventing allergies, asthma, and eczema. Laboratory studies have been hopeful, but there are not enough studies in humans yet for experts to make any specific recommendations.
Consider talking to your allergy specialist about whether probiotics may be useful to you or your child.