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Tree Nut Allergies

by Antony Ham Pong, MBBS

Dr. Ham Pong is a lecturer in the department of pediatrics, University of Ottawa, consultant, Children's Hospital of Eastern Ontario, and committee member, Regulatory Review Project 19 (labelling of food causing severe adverse reactions in Canadians), joint Agriculture &
Agri-Food and Health Canada Commitee, Ottawa, Ontario. He also has a private practice in allergy.

Tree nut allergies are common potentially life-threatening food allergies. They are often lifelong. Tree nuts may belong to different food families which are unrelated to each other and tree nuts are not related to peanut. Peanut allergic people can often eat tree nuts and tree nut allergic allergic people can often take peanuts. However, some allergic individuals may be allergic to both peanut and tree nuts. In addition, you can be allergic to some but not all tree nuts. Almond seems to cause the least problems of all common tree nuts.


Walnut: walnut, pecan Birch: hazelnut, filbert, hickory nut
Mango: pistachio, cashews Plum: almond
Legythis: brazil Macadamia
Beech: beechnut, chestnut

Nuts may be found as a hidden, unlabelled part of a food because of accidental cross-contamination during manufacturing. Allergic reactions are often caused by eating unlabelled foods, by not checking food labels properly for presence of nuts, or from foods which contain hidden unlabelled nuts. Nuts may be used in many of the foods that people like to eat. The most common types of foods causing allergic reaction due to nuts are chocolates, cookies, candies, granola bars, ice cream.
Special occasions such as Easter, Halloween, Christmas and birthday parties are more dangerous for children with nut allergies because there is much more likely to be nut containing foods eaten, and because it is more difficult to supervise children properly. In addition, usual common sense precautions may be forgotten in the excitement. At school, allergic reactions to nuts can happen if children share foods or a parent sends foods containing nuts, e.g., muffins, as a treat for the whole class.

What may contain tree nut?
- chocolate, candies, cookies, desserts, sweets, almond paste, donuts, sundaes, cereal, milkshakes, granola bars, trail mixes, pesto sauce, European chocolates, muesli
- suntan lotion, shampoo, nut shells, bath oils
- popcorn and speciality cheese spreads
- gianduja (chocolate and chopped toasted nuts)
- speciality coffees, liqueurs
- small animal food e.g., hamster, gerbil

What contains walnut (grenoble, noix royal) / pecan (pecan)?
- pecan pie, walnut containing muffins
- Crosse & Blackwell Worchestershire sauce
- AIM herbal fiber blend, pesto sauce, pralines, walnut oil, "Turtles" chocolates

What contains hazelnut / filbert (noisette)?
- Nutella, nougat, Toblerone chocolate bars, hazlenut liqueur, Frangelico liqueur, hazelnut coffee

What contains pistachio (pistache) / cashew (cajou)?
- cashew butter, pistachio ice cream, chicken with cashews

What contains almonds (amande)?
- marzipan, almond mocha, almond paste, almond guy ding, trout almondine, pure almond extract (artificial is okay), amaretto

What can happen during an allergic reaction to nuts?
An allergic reaction to a food usually begins within minutes but may be delayed for 2-4 hours and usually lasts less than one day. The more severe the allergy, the smaller the amount required to cause a reaction. Typical immediate allergic reactions to foods include hives or blotching around the mouth which may spread to the rest of the body, immediate runny nose, sneezing and itchy water eyes, coughing, choking or gagging, wheezing and trouble breathing, and cramps, vomiting and diarrhea. The allergic reaction can stop at any stage, or may progress to anaphylaxis and death. Anaphylaxis is a severe allergic reaction which involves several parts of the body and can lead to death.

A food does not have to be eaten to cause an allergic reaction but eating it does cause greater amounts to get into the body and usually causes the most severe reactions. Hives can occur on skin contract with an allergenic food. If the food goes into the wet surfaces, e.g., through a cut in the skin, or at the lips (e.g., being kissed by someone who has eaten nuts), or in the eye, severe reactions can occur.

Do I have to avoid other nuts?
You do not have to avoid other nuts if you are only allergic to one family of nuts. See above chart of nut families.

How do I treat an allergic reaction on eating nuts?
Anyone with severe nut allergy should use their EpiPen immediately when they begin to have reactions to eating nut accidentally, even if the reaction initially is minor.
This is important to prevent anaphylaxis, the most severe form of an allergic reaction. People who delay treatment with Epinephrine are more likely to die. EpiPen therefore should always be immediately close at hand, i.e., not in the locker, in the car, in the hotel room, or next door. A person with asthma is more likely to have a fatal food reaction. An allergic reaction, especially anaphylaxis, can recur 4-8 hours after initial treatment. It is important to go to the hospital immediately for further treatment and to be observed for several hours after.
If an allergic reaction to nuts begins, use EpiPen immediately as soon as any allergy symptoms develop! Take patient to hospital immediately, preferably by ambulance.

I have eaten foods labelled "may contain nuts" without any problems. Should I still avoid them if I am allergic to nuts?
Definitely avoid them! Companies are allowed to use "may contain nuts" if they cannot guarantee that a food they are producing is free of nuts, usually because nuts are being used in the same machines for other foods. A company that makes similar foods with and without nuts, may have difficulty cleaning the machines in between making the different foods, or packages may be mislabelled. These food manufacturing machines were designed many years ago, and were never designed to be taken apart and cleaned properly. In addition, some of these machines cannot be cleaned with water. Therefore it is quite likely that when a food with nuts is put through the machine, traces of nuts remain on the machine. The first batches of foods made without nuts that go through the same machine will likely contain trace of nuts. Batches of foods done much later are less likely to contain traces of nuts but you cannot be sure which batch of food you are eating. Therefore they should be avoided. This cross-contamination is most likely to occur with cookies, candies, cereals, chocolate, ice cream, dried soups and nut butters.

What about seeds, tropical oils, exotic nuts?
Foods such as water chestnut, pine nut (pignolia or pinyon nuts), coconut, nutmeg do not need to be avoided by nut allergic people unless they are also allergic to these foods. However, allergies to these foods are uncommon. Palm oil and tropical oils do not need to be avoided. Seeds, e.g., sesame, sunflower, poppy, mustard, safflower, canola, do not need to be avoided unless you are allergic to these as well.

I have had only a mild reaction to nuts in the past, and have never had breathing difficulties. Why do I need an EpiPen?
Nut allergy is usually potentially life-threatening and life-long. Even if mild allergic reactions have occurred in the past, severe reactions can still occur with the same amount of food, i.e., the allergy can worsen without warning. Do not also expect that you will have the same amount of time or warning before the reaction occurs as in the past. Therefore EpiPen should be available at all times.

What foods are more likely to contain undeclared nuts?
Chocolate and mint ice cream are most likely to contain undeclared nuts since leftover ice cream can be added to these without changing the flavour. See list above (what may contain nuts). European chocolates are allowed to be made with leftover chocolate which may contain nuts and may not be declared.

How can I tell if my nut allergy is "anaphylactic"?
Many tree nut allergies have a potential for anaphylactic reactions. Anaphylaxis is the most severe form of an allergic reaction as described below. Even a mild food allergy can cause anaphylaxis if enough is eaten. Once you have been prescribed an EpiPen, it means that you have the potential for life-threatening or are "anaphylactic". Whether anaphylaxis will occur depends on how allergic a person is, how much of the food is eaten, how early treatment is started, whether EpiPen is given, and whether the person is having an asthma attack at the time or has chronic asthma.

Are nut oils safe?
Most tree nut oils probably contain enough allergenic protein to cause allergic reactions. These are cold pressed (unprocessed, extruded or expelled) oils and are not safe for nut allergic people.

* These have resulted in deaths

  1. Eating unlabelled foods*. If in doubt, don't.
  2. Unpackaged foods, e.g., a cookie jar, may contain traces of nuts from previous nut containing cookies. Another cookie taken from that jar may contain traces of nuts on it. Bulk foods, and buffet meal may also be dangerous because of cross contamination. Free cookies at stores.
  3. Contamination during preparation, e.g., a cutting board used to cut 2 foods such as chicken and fish -- the chicken served to a fish allergic person or the same board or knife to slice or grind nuts. Using the same oil to fry different foods, or the same batter for different foods, or the same frying utensils for different foods without washing in between can all cause cross contamination.
  4. Grinding specialty nut flavoured coffees in a coffee grinder. Baking muffins with and without nuts if leftover batter is used for the other muffins or if the baking pans are not properly cleaned. Contamination during serving, e.g., sauces mixed by spillage; the same scoop used to take scoops of different ice creams, some of which may contain nuts; a knife used to cut a nut containing dessert and used to cut another dessert.
  5. Relying on someone who does not know but who tells you the food is safe e.g., another child, or someone who did not prepare the food e.g., waiter or salesclerk, airline steward.
  6. Trying a food to see if you are "still allergic" especially with anaphylactic allergy.
  7. Tasting a food carefully to see if it is safe or is not dangerous.*
  8. A change in the way a usual food is made, e.g.., a change in the ingredient list without any obvious change on looking at the container. A new chef at a restaurant may change the recipe and add a "secret ingredient".*
  9. Candy machines may have different foods at different times and candies may be contaminated with traces of nuts if there were nuts in the dispensing machine before.
  10. Be aware of unusual sources of allergenic foods. See list of "what may contain nuts".
  11. Non-food sources of nuts e.g., bags made with nut shells, interactive museum displays made with nut shells, small animal food e.g., hamsters, gerbils.

Further suggestions:
For further information, we strongly recommend you become a member of:

- AAIA, Box 100, Toronto, Ontario M9W 5K9, Toll-free call 1-800-611-7011. Email [email protected] Web site:
- Food Allergy Network, 10400 Eaton Place Suite 107, Fairfax, VA, USA 22030-2208. Toll-free call 1-800-929-4040. Web site:


Anaphylaxis is the most severe form of allergic reaction. It may occur with a food, drug or insect sting. Evan a trace amount of food can cause a severe allergic reaction. Anaphylaxis is an allergic reaction occurring over many parts of the body and can lead to death. Anaphylaxis can occur minutes after taking a food, or may occur several hours later. Death can also occur immediately or be delayed for several hours. How an allergic reactions begins does not necessarily tell you that anaphylaxis will or will not occur.

Features of anaphylaxis are:

  • swelling of the upper airway causing trouble breathing, croup like symptoms, and suffocation
  • swelling of the lips and tongue with trouble swallowing and breathing
  • runny nose, nasal congestion, sneezing, itchy watery eyes
  • skin eruptions such as hives or redness. Itchy anywhere
  • constriction of the lower airways with wheezing, asthma and cough.
  • dizziness and feeling like dying. Low blood pressure, shock.
  • nausea, cramps, diarrhea and vomiting

Terms of Use: The information on this site does not constitute medical advice and is for your general information only. We cannot be held responsible for anything you could possibly do or say because of information on this site.   Consult your family physician or allergist for specific questions or concerns. 


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