Tree Nut Allergies – Causes, Signs and symptoms

Tree Nut Allergies


A tree nut allergy is when a person has an allergic reaction to the proteins found in tree nuts. Tree nuts are large, edible seeds of trees. When an allergic person comes into contact with a tree nut protein, (usually by eating, but less commonly by touching or inhaling the protein) the immune system triggers an allergic cascade. This reaction has the potential to be deadly.

There is no cure for a tree nut allergy. The only effective way to prevent an allergic reaction is the complete avoidance of tree nuts and foods with tree nuts or its products (e.g., nut oils).

There are many different kinds of tree nuts. Some common tree nuts are almonds, cashews, pecans and walnuts. People who are allergic to one type of tree nut may also be allergic to another type. People who are allergic to tree nuts may also be allergic to peanuts, though it should be noted that peanuts are not actually nuts, but a type of legume (bean).

According to the American Academy of Allergy, Asthma and Immunology (AAAAI), about 3 million Americans are allergic to tree nuts and/or peanuts. These allergies are severe enough to kill more than 100 people every year.

Symptoms of tree nut allergies usually include:

  • Swelling
  • Hives
  • Itchiness
  • Redness
  • Nausea
  • Stomach pain
  • Wheezing
  • Runny nose
  • Tingly tongue

Anyone who suffers from a tree nut allergy is susceptible to the severe and potentially deadly allergic reaction known as anaphylaxis. Therefore, individuals with tree nut allergies may be advised to carry an epinephrine shot with them at all times.Medications such as antihistamines may be used to provide relief from less severe symptoms of allergic reactions. However, these drugs are not an acceptable alternative to epinephrine.

About tree nut allergies

A tree nut allergy is a potentially deadly type of food allergy. It involves an allergic reaction triggered by the proteins in tree nuts. Tree nuts are the hard, edible seeds of some trees. Tree nuts and their products (e.g., nut oils) are a common food type and are also found in a number of nonconsumable products ranging from shampoos to topical creams.

The most common tree nuts are:

  • Almonds
  • Beechnuts
  • Brazil nuts
  • Cashews
  • Chestnuts
  • Filberts
  • Hazelnuts
  • Hickory nuts
  • Macadamia nuts
  • Pecans
  • Pine nuts (Pignoli nuts, Pinion)
  • Pistachios
  • Walnuts­­

It should be noted that not all foods with the word “nut” in them are actually tree nuts. For example, peanuts are actually legumes (bean) and are not a type of nut, though people with tree nut allergies may be allergic to peanuts as well.

In addition, nutmeg is a spice, water chestnuts are fruits, ginger nut is a type of cookie and coconut is a fruit. However, people who suffer from severe tree nut allergies may in rare instances experience allergic symptoms when consuming nutmeg or coconut.  

According to the American Academy of Allergy, Asthma and Immunology (AAAAI), about 3 million Americans are allergic to tree nuts and/or peanuts. These allergies are severe enough to kill more than 100 people every year.

Individuals allergic to tree nuts who have been exposed to tree nut proteins will usually begin to experience symptoms immediately, though they can also begin several hours later. Symptoms can also recur hours after the initial reaction subsides. Symptoms typically include swelling, hives, itchiness, redness, nausea and stomach pain. Severe reactions can result in anaphylaxis, leading to life-threatening anaphylactic shock, which includes difficulty breathing and a dangerous drop in blood pressure.

Tree nut allergies can trigger an allergic cascade that includes the following steps:

  • The immune system responds when a tree nut protein enters the body. This usually occurs by eating tree nuts, their components or traces of tree nuts. However, in some individuals it can also occur through skin contact or even inhaling tree nut fumes (usually released during cooking).
  • The immune system reacts by misidentifying tree nut proteins as a dangerous substance. To combat the perceived threat, the body triggers the release of immunoglobin E (IgE) antibodies.
  • The IgE antibodies trigger the release of histamines and other chemicals from mast cells and basophils. The histamines and other chemicals are responsible for the most common allergy symptoms.

Tree nut allergies can be triggered by a very tiny amount of tree nut protein – much less than for any other type of food allergy, except peanuts. Some highly sensitive individuals can have an allergic response simply by kissing or having skin-to-skin contact with another person who has recently eaten tree nuts.

Thermal and chemical treatment of tree nuts (as occurs with cooking or processing) is not effective at reducing the strength of tree nut allergens. This differs from other food allergies, in which cooking or chemically treating foods tend to reduce the allergic response triggered.

The effect of tree nuts on young children, especially infants, is still being studied. Some research suggests that breastfeeding mothers who eat foods associated with allergies (including tree nuts, peanuts, milk, eggs and many others) may pass on exposure to these allergens through their milk. These studies seem to suggest that some infants become sensitized to tree nut allergens at an early age. Conversely, other research has found evidence that the transmission of food allergens can be beneficial, allowing infants to build up a tolerance to the allergen that is likely to preventfutureallergic reactions. More clinical research is needed before the medical community conclusively reaches a consensus on this issue. It is important for new mothers to consult with a physician before changing their diet. In some cases, as with peanuts, a food may not be essential if the nutrients are easily obtained elsewhere.

Potential causes of tree nut allergies

A tree nut allergy can be triggered by even a tiny amount of nut protein in the ingredients of a consumed food. Sensitive individuals need to constantly avoid products or processed foods that contain tree nuts or traces of nuts. Common foods and ingredients that contain or may contain traces of tree nut proteins include:

  • Marzipan (almond paste)
  • Nougat
  • Nut butters (such as cashew butter and almond butter)
  • Nut oils
  • Used oils (that may have been used to fry food containing tree nuts)
  • Nut meal
  • Nutmeat
  • Nut paste
  • Nut extracts (almond extract)
  • African, Chinese, Malaysian, Mexican, Thai, Vietnamese and other ethnic dishes (these traditionally include tree nuts or peanuts)
  • Candy (chocolate)
  • Cookies, pastries and other baked goods
  • Crackers
  • Grain breads
  • Frozen deserts
  • Some cereals including granola, muesli and fruited cereals
  • Salad dressing
  • Gravy
  • Pesto
  • Sauces (e.g., barbecue, bouillon, curry, Worcestershire)
  • Chili
  • Stuffing
  • Mandelonas (peanuts soaked in almond flavoring)
  • Egg rolls
  • Doughnuts
  • Health food bars
  • Cakes (especially carrot cake, pumpkin cake or pie and fruit and nut rolls)
  • Praline
  • Baking mixes
  • Certain vegetarian dishes

Shampoos, conditioners, soaps, lotions and cosmetic creams may also contain tree nut proteins. Sensitive individuals can experience an allergic reaction to these substances by absorbing the tree nut protein through the skin.

There may be ingredients that are cross-contaminated by the machinery in factories or the utensils and appliances in homes and restaurants. In some cases, food packaging may include a statement that the food was processed on equipment that also processes foods containing nuts. However, this statement is not required to appear on food labels by the U.S. Food and Drug Administration. As of January 2006, manufacturers have been required by law to list specific tree nut ingredients used to make packaged goods. When in doubt about a product, consumers are encouraged to contact the manufacturer. People with allergies need to check and recheck ingredients habitually. Sometimes minor ingredients or manufacturing locations change without any formal announcement.

Some people are very responsive to even trace amounts of tree nut proteins. For these people simply touching or kissing another person who has recently consumed nuts can induce an allergic reaction or life threatening anaphylaxis.These sensitive individuals must be very careful not to have skin contact with any type of nut product and should also be careful not to inhale the fumes produced by cooking nuts. Inhaled tree nut fumes can cause symptoms associated with allergic rhinitis (hay fever) in some individuals.

Some types of seeds have been known to cause allergic reactions in people who are sensitive to tree nuts. As tree nuts are basically large, edible seeds, it may be best for a person with a tree nut allergy to be suspicious of all seeds in general. It may be prudent to specifically avoid:

  • Sesame seeds
  • Poppy seeds
  • Sunflower seeds
  • Pine kernels

Related allergies and conditions

People allergic to certain types of tree nuts may also be allergic to other types of tree nuts – a condition known as a cross-reaction. People allergic to tree nuts may also be allergic to peanuts. Because peanuts are not technically in the same food group (they are a type of legume, not a nut), when both types of allergies occur it is sometimes called coincidental allergies. The relationship between different types of nut allergies, however, is not completely understood. Anyone allergic to tree nuts should use caution when consuming any type of nut or peanuts.  

Some tree nut-allergic individuals may find they also suffer from oral allergy syndrome, which is characterized by an itching, tingling or swelling in the lips, tongue, palate or throat after eating certain foods. Usually, these symptoms occur due to a similarity between a specific type of substance in certain foods (certain fresh fruits and vegetables) and certain types of pollen.For example, melons have been associated with producing oral allergy syndrome in people with ragweed pollen allergies.

Individuals who have exhibited a history of allergies, eczema or asthma are more likely to have a tree nut allergy. These individuals are also more likely to have a severe or life-threatening reaction, such as anaphylactic shock.

Several related conditions may be mistaken for a tree nut allergy. These include:

  • Food intolerances. These conditions involve the body’s inability to breakdown specific food substances (such as lactose by people with milk intolerance) – rather than an allergic response to the food in question. With lactose intolerance, for example, a person lacks sufficient amounts of the enzyme lactase, making it difficult to break down the lactose in milk.
  • Food poisoning. Symptoms of food poisoning can also imitate an allergic reaction. But, while the symptoms might appear similar, the body is not producing an actual allergic reaction in these instances. Rather, it is responding to harmful bacteria or other toxins within contaminated or spoiled foods. Reactions can be severe and may therefore be confused with food allergies.
  • Additive sensitivity. Food additives are substances added to food for better preservation, taste and color. Some people have reported experiencing reactions to certain additives when ingested (e.g., MSG, sulfites). More research is needed on this subject before the medical community can confirm or reject this condition.
  • Irritable bowel syndrome (IBS). A disorder in which the large intestine does not function normally, leading to cramping, abdominal pain, bloating, constipation and/or diarrhea. Because specific types of food will sometimes trigger IBS symptoms, this condition may be confused with a tree nut allergy.
  • Other gastrointestinal conditions. Some kinds of cancers and ulcers of the gastrointestinal tract can produce symptoms similar to those experienced with tree nut allergies. These symptoms can include vomiting, diarrhea or cramping abdominal pain that gets worse when eating.
  • Stress or psychological issues. While the relationship between stress and allergy symptoms is not entirely clear, some individuals may feel sick simply by thinking about a certain type of food.

Signs and symptoms of tree nut allergies

Exposure to tree nuts can trigger a multitude of symptoms in sensitive individuals. Symptoms typically appear within minutes of eating a tree nut or tree nut product, although some reactions are known to occur up to four hours after consumption and could reoccur hours later with a second wave of symptoms following the initial attack. Symptoms of an allergic reaction to tree nuts may include:

  • Tingling feeling in the lips and mouth
  • Itchy hives (urticaria), primarily when nuts make skin contact
  • Swelling (angioedema), primarily when nuts make skin contact
  • Vomiting or diarrhea
  • Cramping stomach pains
  • Dizziness, faintness or unconsciousness
  • Shortness of breath
  • Swelling in the throat (causing swallowing or breathing difficulties)

Allergic reactions to tree nuts can range from mild anaphylaxis (generalized allergic reaction involving two or more body systems) to severe and potentially life-threatening anaphylactic shock. There is no way to predict the severity of reaction when a person with food allergies ingests the problem foods. Therefore even people experiencing mild symptoms should immediately contact a physician or seek medical treatment. Some highly sensitive individuals will react to just a small portion of tree nuts with anaphylactic shock. This life-threatening condition is characterized by constriction of the air passageways and a dangerous drop in blood pressure.

Cashew nut shell oil is known to cause contact dermatitis. The cashew tree belongs to the same family of plants that include poison ivy, poison oak and poison sumac. There are a number of reports of allergic contact dermatitis following ingestion of cashew nut butter, cashew nut pesto and cashew nuts – all that had been contaminated with cashew nut shell oil.

Diagnosis methods for tree nut allergies

The methods used to diagnosis tree nut allergies are very similar to those used to diagnose other food allergies. Physicians will generally start by asking a patient about their medical history and will perform a physical examination to rule out any conditions with similar symptoms. To better determine the allergen, the physician will often have patients keep a food diary of everything they eat over a period of weeks or months. This will help demonstrate a correlation between a certain type of food and the onset of allergy symptoms.

Other diagnostic methods may include:

  • Skin test. This test involves scratching, pricking or injecting an individual’s skin with a tree nut extract. If the tested area reacts with redness or swelling, it may indicate an allergic response. This test can be dangerous for individuals with severe tree nut allergies.

  • RAST (radioallergosorbent test). This blood test allows a laboratory to detect antibodies in a sample of the patient’s blood that may indicate a tree nut allergy. It can be safely used on people who have severe allergic reactions.

  • Blinded food challenge test. This is considered the most effective way of determining the cause of a food allergy because it supplies the most convincing results. Different foods are placed within capsules to hide their identity. The patient consumes the capsules and the physician looks for signs of an allergic reaction. This type of test is time-consuming and is often reserved to confirm suspicions that a patient’s symptoms are not caused by a food allergy. This type of test should only be performed in the presence of a physician who can treat anaphylaxis.

  • Elimination diet. This method involves removing tree nuts from an individual’s diet for several weeks to see if allergic reactions persist. If symptoms stop, it can be presumed that tree nut allergy was the cause. The food may then be briefly reintroduced to the patient’s diet in a controlled, clinical setting. If symptoms resume, the diagnosis of tree nut allergy is confirmed.

Treatment and prevention of tree nut allergies

The only effective prevention of an allergic reaction to tree nuts is the complete avoidance of tree nuts and tree nut products. This means constant vigilance when buying food in a grocery store, eating at a friend’s house or eating out at a restaurant. Individuals with tree nut allergies must always check the labels of the foods they purchase and inquire about food preparation and ingredients when they are eating away from home. Accidental exposure to tree nut proteins can be fatal.

Because eating just a trace amount of tree nut protein can trigger an allergic response, allergic individuals must be very careful of what types of foods they consume. Many types of foods contain tree nuts. Allergic individuals should educate themselves on some of the other names of products that may contain tree nuts. For example, gianduja is hazelnut-flavored chocolate and caponata is an eggplant-based relish that may contain pine nuts.

New food labeling laws which took effect in January 2006 may make it easier for people to determine if a food item contains any tree nuts or tree nut products (e.g., tree nut oil). If tree nuts are used to make a packaged product, the manufacturer must clearly list the specific type of tree nut it contains.

People need to be careful of not only ingredients, but food preparation methods as well. Kitchen utensils or factory equipment that come into contact with tree nuts can accidentally spread tree nut molecules into other foods when not properly cleaned between uses. Manufacturers may disclose on package labels whether products have been processed on equipment also used to prepare tree nut products. Many manufacturers offer toll-free customer service lines to answer questions regarding their products. Commonly printed on product packaging, these phone numbers enable individuals to inquire about ingredients as well as other concerns.  

Tips to avoid exposure to tree nuts while dining out include:

  • Keep restaurant orders simple. Baked and broiled items and single food items are better choices than items with many ingredients. For example, a baked potato is a better choice than potato souffle, which may contain unknown ingredients.

  • Avoid creams, dressings, sauces and toppings.

  • Avoid salad bars and buffet lines. Serving utensils are often used interchangeably in these serving situations.

  • Avoid ethnic foods that usually contain tree nuts (e.g., African, Asian).

  • Take special note when ordering dessert. Nuts may be used, even if not indicated on the menu.

  • Avoid asking the waiter or waitress about the ingredients used in the dishes. Only the owner or the person overseeing the kitchen should be approached.

Epinephrine is a synthetic form of adrenaline that, when injected, works as a powerful bronchodilator, reversing the symptoms of anaphylactic shock. It opens breathing tubes and restores normal respiration quickly. It also raises blood pressure. A physician may recommend that patients carry an injection of epinephrine with them at all times and understand how to self-administer the drug. A medical alert bracelet or necklace may also be recommended.

In the case of children with tree nut allergies, schools, daycare facilities and clubs all need to be informed of the child’s condition. Schools should work closely with the parents to make sure the child does not accidentally come into contact with tree nuts in the cafeteria or the classroom. Babysitters, grandparents, and the parents of friends should all be advised of the child’s allergy and should be taught emergency treatment procedures.

Activated charcoal may help reduce the severity and progression of an allergic reaction to tree nuts. The therapy works by binding to the major allergens in the nut, blocking the allergens from interacting with the immune system and preventing allergy symptoms. This type of therapy may not be suitable for treating a tree nut allergic reaction by itself. It should be used only after another type of more effective treatment (e.g., epinephrine) has been administered.

In some cases, antihistamines and other allergy medications may also be used to treat less severe symptoms of allergic reactions.

Questions for your doctor regarding allergies

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about tree nut allergies:

  1. What tests will you use to determine if I am allergic to tree nuts?
  2. How will I know I am having an allergic reaction to tree nuts?
  3. What treatment options are available to me?
  4. Is it safe to consume a small amount of tree nuts?
  5. What should I do if I accidentally consume tree nuts?
  6. Are my children more likely to develop tree nut allergies because I have the condition?
  7. Is my child likely to outgrow their tree nut allergy?
  8. How will you determine if the tree nut allergy has been outgrown?
  9. What products commonly include tree nuts?
  10. What terms should I look for when reading an ingredient label?
  11. Can I still eat at restaurants?
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