Peanut Allergies, Soybeans, and Legumes

If you're allergic to peanuts, which are a legume, you probably don't need to avoid most other legumes such as soybeans, peas, and beans.

However, your allergist may advise you differently depending on your individual test results and family medical history. In addition, there's one legume—lupin—that you most likely should avoid, since there's a higher likelihood of a reaction to lupin in people who are allergic to peanuts.

Are Peanuts Nuts?

Walnuts, pecans, cashews, hazelnuts, and almonds all grow on trees and are classified as tree nuts. Many people believe that peanuts are also a nut—after all, they have the word "nut" in their name. However, that's not correct.

Peanuts are in fact a member of a plant family called legumes. In general, legume pods can contain edible seeds. Other members of the legume family include peas, beans, and soybeans.

Though peanuts and tree nuts have many botanical differences, they are often grouped together because of their similar nutrition profiles and dietary uses. While some people can be allergic to both peanuts and tree nuts due to shared proteins, the majority of people who have a peanut allergy do not need to avoid tree nuts.

Even though peanuts are more closely related botanically to legumes than they are to tree nuts, people who have peanut allergies are at a higher than normal risk of tree nut allergy. An allergist can help determine whether you need to avoid any tree nuts and if so, which specific tree nuts you should avoid.

Potential Legume Allergies

There is some cross-reactivity between peanuts and other legumes, although the majority of people who have a peanut allergy can eat most other legumes.

If you have a peanut allergy, your allergist may have you take a skin prick test to see how your body reacts when exposed to allergen proteins that are found in other legumes. Often, the test will yield a positive result for legumes that you have never had any trouble eating before.

In one study, 35% of people who had a peanut allergy tested positive for allergies to other legumes. However, just 5% of people had allergic symptoms upon exposure to those legumes. As a next step, your allergist may conduct an oral food challenge to narrow down which legumes, if any, you should avoid eating.

Lupin May Cause a Reaction

One type of legume, lupin, may pose higher risks than other legumes for those who have peanut allergy. Lupin (also known as lupine) is a legume that's common in Europe, where it's used as flour in baked goods.

Lupin is becoming more common in the U.S., where lupin flour is used occasionally in gluten-free pasta and baked goods.

Other products that may contain lupin are:

• Alternative meat products, such as vegetarian sausage
• Dairy-free ice cream or products that substitute lupin for soy or cow's milk
• Deep-fried vegetables, such as onion rings or fried pickles
• Lupin hummus
• Tempe, crumb, or lupin flakes
• Pre-packaged foods

Studies have shown that up to half of people with peanut allergies can be sensitized to lupin (have a positive allergy test to lupin), but not all of these people will react to it. Therefore, you should talk to your healthcare provider before trying lupin and watch for it on food labels. You may also see it labeled as lupin flour, lupinus, lupine, lupini, or lupine beans.

Soy Allergies

For adults, soy allergy as an isolated allergy is not common, nor is soy-related anaphylaxis. More often, soy allergy is detected in infants and is typically outgrown by the time children are 10 years old.

The allergen triggers in soy and peanuts are not related, and having an allergy to soy does not increase your risk of having a peanut allergy or a tree nut allergy.

It's common for people who have a peanut allergy to test positive for soy allergy as well, but this does indicate that they will necessarily have allergic symptoms when exposed to soy.

Soy Formula and Peanut Allergies

In 2020, the U.S. Department of Agriculture (USDA) and Health and Human Services (HHS) released dietary recommendations for infants and children under the age of 2. According to the guidelines, there is no evidence to suggest that the introduction of potentially allergenic foods should be delayed. For infants with severe eczema, egg allergy, or both, feeding age-appropriate peanut-containing products as early as 4-6 months of life can reduce the risk of developing peanut allergy.

Frequently Asked Questions

Can I eat other nuts if I am allergic to peanuts?

Maybe, but there’s a chance you are allergic to other nuts if you’re allergic to peanuts. Between 25 and 40% of people diagnosed with a peanut allergy are allergic to at least one other nut such as almonds or cashews. Your allergist should do a test to check whether you react to these other nuts, known as tree nuts.

Why are more people developing peanut allergies?

Researchers are not completely sure what has caused a rise in peanut allergies. Theories that have been investigated include changes in childhood vaccinations, an increased focus on hand washing, and delaying the introduction of peanuts into a baby’s diet. More research is needed to understand these and other factors.

What are tree nuts?

These are really seeds of fruit-bearing trees. Unlike most types of fruit in which you eat the soft edible outer skin, the outer part of a tree nut is too hard to eat (think of a pistachio shell). Instead, we can eat the seed inside, the nut. Types of tree nuts include almonds, hazelnuts, cashew nuts, macadamias, and walnuts.

A Word From Verywell

While most infants and children with peanut allergy can tolerate soy, some may also be allergic to soy or other legumes. If it is not clear which foods need to be avoided, an allergist can offer guidance based on clinical history and test results.

In general, the American Academy of Pediatrics recommends that​ babies at high risk for developing food allergies be exclusively breast-fed for at least four months. Breastfeeding beyond three to four months protects from wheezing for up to two years and any longer duration of breastfeeding protects against asthma even beyond age five years. If that's not possible, pediatricians recommend using partially or extensively hydrolyzed formula.