Although many peanut allergies aren't serious, some can be life-threatening, so it's a smart idea to think about potential cross-reactivity with related foods. Soybeans and peanuts are both legumes, and while not everyone who has sensitivity to peanuts has the same reaction to soybeans, it's not uncommon to exhibit an allergic reaction to both.
Peanut and Soy Reaction
Writing for the Calgary Allergy Network, Dr. Anthony Ham Pong, a Canadian allergist, said that peanut allergy is the most common life-threatening food allergy in children. Soy is botanically related to peanuts, as well as all other legumes, including beans, peas and carob, according to AllergicChild.com. However, the relation does not indicate that being allergic to one will guarantee an allergy to the other.
Cross-Reactivity
Cross-reactivity refers to a mistake the immune system makes -- a protein or compound is mistaken for a known allergen. Some people may experience cross-reactivity with peanuts and soy and exhibit allergic reactions to both. However, Dr. Ham Pong does not recommend avoiding soybeans if you have a peanut allergy. "Soy is very unlikely to cause an allergy in peanut allergic people," he wrote. "Most peanut allergic people can eat other legumes, even if they have a positive skin test to these other legumes. However, a positive skin test [indicates] some chance of developing an allergy to the legume later."
Statistics
New Zealand's Auckland Allergy Clinic has conducted a number of studies researching cross-reactivity among legumes in children. Cross-reactions have been uncommon. In a study that included 113 children, less than 1 percent were allergic to both peanut and soy. Skin tests showed that about a third of children demonstrated a positive skin response to soy, but only one child exhibited a clinical reaction to it.
Symptoms
If you are allergic to soybeans, as well as peanuts, your body will let you know by showing symptoms. According to Dr. Ham Pong, you're likely to see a reaction within two to four hours after eating soybeans. Symptoms may include hives, a rash, runny nose, watery eyes, coughing, difficulty breathing, cramps, abdominal discomfort or anaphylaxis.
Considerations
If you are allergic to peanuts and suspect that you may also have an allergy to soybeans, you can see an allergist and have a test to get a conclusive result. However, keep in mind that while a positive skin test may demonstrate some intolerance, the majority of people with peanut allergies are still able to eat soybeans and soy products with no negative clinical effects.
