Tree Nut Allergies: What Are They?

in Basics, Food Allergy, Peanut & Tree Nut
Tree nut allergies are one of the most common types of food allergies in North America.Photo: Getty

Tree nut allergies are one of the most common types of food allergies in North America today.

When someone with tree nut allergies consumes their allergen, even a trace amount, that person is at risk of a severe allergic reaction, called anaphylaxis. An anaphylactic reaction includes more than one of the body’s systems, such as the respiratory tract, gastrointestinal tract, the skin and cardiovascular symptoms.

Symptoms of Allergic Reaction to Tree Nuts:

  • tingling in the mouth.
  • swelling of the face, lips, tongue or throat.
  • itchy skin, hives or skin redness.
  • breathing difficulty or wheezing.
  • vomiting or diarrhea, abdominal cramps.
  • faintness due to a sudden drop in blood pressure.
  • anxiety; feeling of impending doom.
  • In a severe anaphylactic reaction, the allergic person can lose consciousness, and is at risk of cardiac arrest or even death.

One of the issues in managing tree nut allergies is that reaction severity can vary greatly. A person may have minor symptoms on one occasion, but anaphylaxis on a next exposure.

Because tree nut reactions can be severe, it is important that a person with this allergy carry an epinephrine auto-injector with them at all times. Research has shown that a small number of people (about 9 per cent) may outgrow their tree nut allergies.

What is a Tree Nut?

Tree nuts are not just one allergen, but in fact a group of allergenic foods that in the U.S. include:

Beech nuts
Brazil nuts
Ginko nuts
Hickory nuts
Lichee nuts
Macadamia nuts/Bush nuts
Pine nuts/Pinon nuts
Shea nuts

What is Not a Nut?

The FDA includes coconut as a tree nut when it comes to food labeling in the United States. However, coconut is not, strictly speaking, a nut. Rather, it is the fruit of a palm tree.

Allergists report that most people with tree nut allergies are able to eat coconut. However, it is possible to be allergic to coconut. Speak to your allergist about whether coconut is safe in your diet.

People often refer to peanuts as nuts, but peanuts are in fact legumes. While many people are allergic to both tree nuts and peanuts, it’s quite common to be allergic to one and not the other.

Nutmeg and water chestnuts are not nuts.

Risks with Peanuts or Other Nuts

Those with tree nut allergies are often advised not to eat peanuts because of the risk of cross-contact during the manufacturing process. This is because nuts and peanuts may be packaged using the same equipment. If you have a tree nut allergy, talk to your allergist about whether you should also be avoiding peanuts.

While tree nuts and peanuts are not relatives, the medical literature shows one-quarter to one-half of people with peanut allergy will also have tree nut allergies.

Most people with nut allergies are not allergic to all tree nuts, but certain pairs will commonly “cross-react.” This is because of similarity in their protein structures. These pairings include pecan and walnut, cashew and pistachio, and almond and hazelnut.

So someone who has had a reaction to cashew will likely also be allergic to pistachio, but may not be allergic to almond or hazelnuts. An allergist can help with determining precise tree nut allergies. As with peanuts, there can still be the practical issue of shared production facilities among differing types of tree nuts. However, some tree nut producers have facilities dedicated to just one or two tree nuts.

For some people, eating nuts such as almonds, hazelnuts and walnuts can set off a tingly, itchy sensation in the mouth, lips or throat. This may not be a true allergy, but in fact, a condition called oral allergy syndrome (OAS).

OAS is a reaction to foods including fruit, vegetables, nuts, spices, legumes and seeds that actually stems from pollen allergies. The structure of some of the proteins in the pollens of birch and alder trees, grass and ragweed are so similar to the proteins in related foods that some people’s immune systems can’t tell the difference. If the birch tree gives you sneezing and congestion, for instance, it’s possible that an apple, carrot or hazelnut might make your mouth itch.

It can be difficult to figure out if you’re having an actual allergic reaction to a food, which can cause anaphylaxis (the serious form of reaction) or if it is OAS. While symptoms for the latter condition are usually milder, Allergic Living strongly suggests a visit to an allergist if you are reacting to nuts of any kind.

Why are Tree Nut Allergies on the Rise?

No one knows for certain why people have more allergies (including tree nut allergies) today than they did in the past. One theory that has gained prominence is the hygiene hypothesis.

This hypothesis states that kids growing up in industrialized countries are not exposed to the level of germs, infections and parasites as kids who grow up in less clean or modern environments. The idea is that the immune system needs these exposures to develop properly, and without them, it is underworked – and begins to develop antibodies to otherwise harmless substances, such as peanuts.

Other theories that attempt to explain a rise in food allergy include insufficient vitamin D, food processing (e.g. roasting of peanuts for peanut butter, rather than fried or boiled peanuts), and the delay of exposure to the allergen in infancy.

Is There a Cure for Tree Nut Allergies?

Currently, there is no cure for tree nut allergies. Scientists are working on ways to “desensitize” patients to some allergens, including peanuts, milk and egg. The most researched and talked about form of desensitization is called oral immunotherapy (OIT). It is now also being studied with tree nuts and early results have been positive.

In this treatment, an allergic child consumes gradually increasing amounts of his or her allergen in an effort to retrain the immune system. Allergists have been able to show considerable success using this method.

Related Reading:
Is Shea Butter Safe with Nut Allergy?
Can You Be Allergic to Just One Type of Tree Nut?