Peanut allergies are very common, affecting about 3% of the population. That incidence makes peanut allergy one of the most common food allergies in children and the third most common in adults. And most of these people are all too familiar with the telltale signs of a reaction.
“Symptoms of a true peanut allergy are obvious and come on quickly,” says Christian Nageotte, M.D., an allergist at Henry Ford Health. “Most people who have it are well aware of their allergy.”
But many people with a peanut allergy may not be aware that it also puts them at higher risk of other food allergies. Dr. Nageotte explains why that’s the case and how you can safely manage multiple food allergies.
What Is a Cross-Reactive Allergy?
When you’re allergic to peanuts, your body can react to certain component proteins the tree nuts contain. Your body mistakenly thinks those proteins are harmful and responds by launching an allergic reaction.
The severity of the reaction depends on how sensitive you are to the proteins. Symptoms can be mild—itchy throat, tingling or swelling in your mouth, wheezing. For people who are highly allergic, symptoms can be life-threatening—difficulty breathing or swallowing, even loss of consciousness. A rapid-onset, severe allergic reaction is called anaphylaxis.
“People often assume that if they’re allergic to peanuts, they will have a similar reaction to other nuts,” says Dr. Nageotte. “But peanuts aren’t nuts—they’re legumes, like soy and other beans.” In fact, up to 28% of people with peanut allergies are also allergic to other legumes.
When you’re allergic to both peanuts and a related food, it’s called a cross-reactive allergy. It occurs because the proteins in the one food you’re allergic to (such as peanuts) are similar to the proteins in another food (such as soybeans). If the body recognizes the proteins as the same, it will mount the same allergic reaction to both.
What Allergens Are Cross-Reactive With Peanuts?
Legumes are the most common foods that trigger a cross-reactive peanut allergy. This category includes soy (such as edamame, tofu and soy milk), chickpeas, lentils, peas and other beans.
Tree nuts (such as almonds or cashews) aren’t related to peanuts, but they contain similar enough proteins that some people are allergic to both. An estimated 30% of people with peanut allergy are also allergic to tree nuts.
You can also have a cross-reactive allergy to non-food allergens. “Some people with peanut allergies may react when exposed to birch pollen,” says Dr. Nageotte. “The cross-reaction can trigger hives but isn’t life-threatening.”
The Importance of Food Allergy Testing
“Many people with peanut allergies display a sensitivity to other foods,” says Dr. Nageotte. “But that sensitivity may not be a true allergy, in which case they don’t need to avoid those foods.”
The only definitive way to determine if you have a cross-reactive allergy is to get tested. “Skin or blood tests can give false positives and lead people to restrict their diets unnecessarily,” he says.
The gold standard for food allergy testing is an oral challenge. During the test, you ingest small, gradually increasing, amounts of the suspected allergen. The doctor closely monitors you and can intervene and treat any allergic reaction.
Managing Cross-Reactive Allergies
Allergy & Immunology at Henry Ford Health
If you’re dealing with a peanut cross-reactive allergy (in yourself or your child), the most important thing is awareness. “You need to read food labels carefully, paying attention to the allergens listed,” says Dr. Nageotte. He also reminds patients to watch for cross-contamination (such as reusing a cutting board where you made a peanut butter sandwich).
You also want to be prepared at all times for the possibility of an allergic reaction. You and your child should always carry an EpiPen® or the nasal spray neffy®. And make sure any caregivers know how to recognize the signs of a severe reaction and how to treat it.
Severely allergic children may benefit from oral immunotherapy, which can reduce symptoms and help them tolerate greater exposure. “With treatment, some kids can tolerate up to 4 grams of peanut protein without a severe reaction,” says Dr. Nageotte.
Many children—up to 20%—outgrow peanut allergies at some point. If your child is allergic, ask your doctor about retesting every few years to check their status.
Peanut and cross-reactive allergies can be frightening, but with the right knowledge and tools, you can manage them safely.
Reviewed by Christian Nageotte, M.D., an allergy and immunology specialist who treats children and adults at Henry Ford Medical Center - Columbus, Henry Ford Medical Center - Fairlane and Henry Ford Medical Center - Sterling Heights.
