Allergen Fact Sheets

Walnut Allergen Facts, Symptoms, and Treatment

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Walnut

Allergies to tree nuts such as walnuts are common and often severe. These types of allergies typically develop by the age of 2, and the number of tree nuts to which a person is allergic may increase with age.1 Roughly 30 percent of people with a tree nut allergy are allergic to more than one nut. And while peanuts are actually legumes, approximately 20 to 30 percent of those with a peanut allergy are also allergic to one or more types of tree nuts.2 In fact, together, peanuts and tree nuts account for 70 to 90 percent of reported food-related anaphylactic fatalities. Prevalence for tree nut allergy varies by age, region, and the definitions used for diagnosis, but it appears to affect .05 to 7.3 percent of the population. And unfortunately, compared to other food allergies, the chances of outgrowing these allergies are lower and restricted to an estimated 10 percent of sensitized individuals.1

The following nine varieties account for the majority of tree nut allergies: walnuts, almonds, pistachios, cashews, pecans, hazelnuts, macadamias, Brazil nuts, and pine nuts.1 Rich in omega 3s, walnuts are actually seeds that provide proteins, fats, antioxidants, and some vitamins and minerals.3

Where are walnuts found?

Although walnuts can be eaten raw and unprocessed and are sometimes used as a paste, they're also found in foods such as yogurts, pizzas, cakes, salads, biscuits, ice creams, and other desserts. Particularly in Middle Eastern countries, walnuts also are combined with dates, grapes, and almonds to create a cake called mamoul.3

The following items may contain tree nuts and seeds:4 baked goods, baking mixes, barbeque and pesto sauces, cereals, chocolates, pralines, crackers, dressings, gravies, flavored coffees, frozen desserts, muesli, nougats, almond chicken, pad thai, chili and trout amandines and giandujas (i.e., chocolate blended with hazel nuts), marzipans (i.e., almond paste), almond milks, nut milks, tree nut oils, spreads (e.g., cheese spreads and chocolate nut spreads such as Nutella, which contains hazelnuts), vegetarian dishes, Indian curries, Asian dishes, pastas, liqueurs (e.g., amaretto and Frangelico), natural flavorings and extracts (e.g., pure almond extract), salads, trail mixes, and snack foods.

Also note that the words "natural flavors" and "botanicals" may indicate the presence of nuts or nut flavorings.5 Asian restaurants can be especially problematic because they often use nuts and seeds in their cuisine, and since pans may be used for multiple meal preparations, there's an inherent risk for cross-contamination.7

Nonfood items that may contain tree nuts include:4 bean bags, bird seeds, cosmetics, hair care products, sunscreens, massage oils, and pet foods.

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Are there other allergens I could be sensitized to?*

Some people with a walnut allergy may also experience symptoms when eating other seemingly unrelated foods. This is called cross-reactivity and occurs when your body's immune system identifies the proteins, or components, in different substances as being structurally similar or biologically related, thus triggering a response. The most common cross-reactivities with walnuts are plant foods, e.g., tree nuts, fruits, soybeans, vegetables, and legumes.

Walnuts and pecans share similar allergenic proteins, so those who react to walnuts may also react to pecans and vice versa.4

If you experience an itchy mouth or ears, scratchy throat, hives on the mouth, or swelling of the lips, mouth, tongue, or throat after eating walnuts or other related fresh fruits, raw vegetables, or tree nuts, you may suffer from Pollen Food Allergy Syndrome (PFAS) also called Oral Allergy Syndrome (OAS). This condition is caused by your immune system's reaction to similar proteins, or components, found in foods and pollens.6 It is quite common, as one study suggests that up to 25 percent of children with allergic rhinitis (aka hay fever) also suffer from PFAS.8 Common pollen allergies that could cause OAS when eating walnuts include tree (e.g., birch), grass, and weed.4

Do I need to avoid all forms of walnut?

Walnut consists of different types of proteins that all have different characteristics and different levels of risk for causing symptoms. Some people may tolerate walnut if it is extensively heated (cooked/roasted), as high temperatures break down the causative proteins. For another patient, walnut should be avoided completely since the protein is stable to heat and it could potentially cause a severe event, also called anaphylaxis. Your specific risk profile depends on which proteins in the walnut you are allergic to.4

*These products may not be approved for clinical use in your country. Please work with your healthcare provider to understand availability.

How do I manage my allergy?

Since accidental ingestion of tree nuts and cross-contamination between nut species are common, eliminating all tree nuts from your diet simplifies allergy management. But to better determine whether you should avoid all tree nuts or only those to which you're allergic, consult your healthcare provider.1 He or she also may recommend a plan that includes the following.9-12

  • Read ingredient labels and "may contain" advisory panels on food and nonfood products carefully, and avoid all foods and products containing any form of the allergen. Note that these lists and panels may not appear on the same side of a product's packaging and that manufacturers frequently change ingredients. If you're unable to obtain a list of ingredients, it's safest to avoid that item.
  • Avoid cross-contamination when cooking by using two sets of cooking and eating utensils, with one exclusively for the allergic individual. Wash all dishes and utensils in hot soapy water between uses.
  • Craft an action plan with a list of steps for you and others to take should you accidentally ingest the allergen. Print out a copy of the plan and carry it with you.
  • Talk with restaurant chefs about your allergy and order food that's simply prepared and void of any form of the allergen. Avoid desserts, as they often contain or have come into contact with food allergens.
  • Plan ahead for traveling to ensure your food allergy will be managed and any emergency medication is always available.
  • Wear a medical ID bracelet identifying the allergen to which you're allergic.
  • Carry any recommended or emergency medication with you at all times.
  • Teach children with food allergies which foods to avoid. Work with caregivers and school staff to eliminate or reduce exposure to the allergen and to ensure they understand when and how to use medication to treat symptoms.

Your healthcare provider may direct you to take one of the following medications:

  • Epinephrine auto-injector when there are signs of an acute severe event, aka anaphylaxis (see below). Ensure your family members know how to administer it in case of an emergency.
  • Antihistamines as a supplement may be useful in relieving mild symptoms (e.g., itch); however, they do not halt the progression of an allergic reaction.
  • Bronchodilator (albuterol) as a supplemental therapy for respiratory symptoms, especially in those with a history of bronchospasm or asthma.

If you're with someone who's having an allergic reaction and shows signs of shock, act fast. Look for pale, cool, and clammy skin; a weak, rapid pulse; trouble breathing; confusion; and loss of consciousness. Do the following immediately:

  • Call local emergency services.
  • Ensure the affected individual is lying down with legs elevated.
  • Administer epinephrine immediately for any obvious signs of anaphylaxis.
  • Check the affected individual's pulse and breathing and administer CPR or other first-aid measures if necessary.

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Common Symptoms

Tree nut allergy symptoms typically occur within minutes of ingestion and can range from hives to anaphylaxis, a potentially life-threatening reaction that impairs breathing and can send the body into shock.2,5 In fact, tree nut allergy accounts for 18 to 40 percent of anaphylaxis cases. This severity is particularly problematic because many people can't recognize tree nuts. In one study, for example, only half of participants with a tree nut allergy correctly identified all forms of the nut to which they were allergic.1

Tree nut allergy symptoms can include:5

  • Abdominal pain, cramps, nausea, and vomiting
  • Diarrhea
  • Difficulty swallowing
  • Itching of the mouth, throat, eyes, skin, or other areas
  • Nasal congestion, runny nose
  • Shortness of breath
  • Anaphylaxis, a potentially life-threatening event

Allergic reactions from tree nuts can also come from cross-reactivity to birch pollen in the form of Oral Allergy Syndrome (OAS), aka Pollen Food Syndrome (PFS) and Pollen Food Allergy Syndrome (PFAS).2,6

Symptoms of OAS can include:6

  • Itchy mouth and hives on the mouth
  • Scratchy throat
  • Swelling of the lips, mouth, tongue, and throat
  • Itchy ears

How do I know if I'm allergic?*

Together with your symptom history, skin-prick testing or specific IgE blood testing can help determine if you are allergic to a particular allergen. If you are diagnosed with an allergy, your healthcare provider will work with you to create a management plan.

*These products may not be approved for clinical use in your country. Please work with your healthcare provider to understand availability.

Is there a risk for a severe event?

Knowing the proteins, or components, within each allergen that are triggering your symptoms can help guide your management plan. With that in mind, and based on your symptom history, your healthcare provider may suggest something called a specific IgE component test, which can help reveal other pollens and foods you may react to.4

Already have your specific IgE component test results?

Your component test results will include the name of the components (a series of letters and numbers). Your healthcare provider will likely review the results with you, but here you'll find an at-a-glance breakdown you can use as a reference. Simply match the component names to the list below to see what they mean in terms of symptom management.4

rJug r 1

  • Usually associated with a risk for severe reactions or anaphylaxis.
  • Stable to heat and digestion; cooked, roasted, and raw walnut may cause symptoms.

rJug r 3

  • Usually associated with an intermediate risk for severe reactions but also with milder symptoms such as Oral Allergy Syndrome (OAS).
  • May cause symptoms due to cross-reactivity with pollens (e.g., Parietaria, ragweed, mugwort, olive, plane tree), plant foods (e.g., peach, apple, citrus fruits, grape, tomato, asparagus, lettuce, etc.), nuts (e.g., hazelnut, peanut), and more.
  • Stable to heat and digestion; cooked, roasted, and raw walnut may cause symptoms.

rBet v 1 (PR-10)

  • Usually associated with mild, localized symptoms, such as OAS, but may also include severe allergic reactions.
  • May cause symptoms due to cross-reactivity to pollens (e.g., birch, alder, hazel, oak, hornbeam, beech), raw plant foods (e.g., strawberry, apple, peach, pear, raspberry, kiwi, celery, carrot, soy, hazelnut, chestnut, tomato), and more.
  • Sensitive to heat and digestion; cooked or roasted walnut may be tolerated.

rBet v 2 (Profilin)

  • Usually associated with mild, localized symptoms such as OAS.
  • May cause symptoms due to cross-reactivity to pollens (e.g., birch, alder, hazel, oak, hornbeam, beech), grass pollen, raw plant foods (e.g., tomato, melon, citrus fruits, banana, pineapple, persimmon, zucchini, tomato), and more.
  • Sensitive to heat and digestion; cooked or roasted walnut may be tolerated.

MUXF3 (CCD)

  • Positive specific IgE for walnut in combination with MUXF3 CCD (Cross-Reactive Carbohydrate Determinant) being the only positive component test indicates that the cause of symptoms may be something other than walnut.

Please note that test results should be interpreted by your healthcare provider in the context of your clinical history. Final diagnosis and decisions on further management should be made by your healthcare provider.

*These products may not be approved for clinical use in your country. Please work with your healthcare provider to understand availability.

  1. Weinberger T, Sicherer S. Current perspectives on tree nut allergy: a review. J Asthma Allergy. 2018 Mar 26;11:41-51. doi: 10.2147/JAA.S141636. PMID: 29618933; PMCID: PMC5875412. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5875412/pdf/jaa-11-041.pdf.
  2. McWilliam V, Koplin J, Lodge C, Tang M, Dharmage S, Allen K. The Prevalence of Tree Nut Allergy: A Systematic Review. Curr Allergy Asthma Rep. 2015 Sep;15(9):54. doi: 10.1007/s11882-015-0555-8. PMID: 26233427.
  3. Şen, Mehmet & Karadeniz, Turan. (2015). The nutritional value of walnut. Journal of Hygienic Engineering and Design. 11. 68. Available from: https://www.researchgate.net/publication/320445322_The_nutritional_value_of_walnut
  4. EAACI, et al. Molecular allergology user's guide. Pediatric Allergy Immunol. 2016 May;27 Suppl 23:1-250. do: 10.1111/pai.12563. PMID: 27288833. (245-254 p.) Available from: http://www.eaaci.org/documents/Molecular_Allergology-web.pdf.
  5. American College of Allergy, Asthma & Immunology [Internet]. Arlington Heights, IL: American College of Allergy, Asthma & Immunology; 2014. Available from: https://acaai.org/allergies/types/food-allergies/types-food-allergy/tree-nut-allergy.
  6. American College of Allergy, Asthma & Immunology [Internet]. Arlington Heights, IL: American College of Allergy, Asthma & Immunology; 2014. Available from: https://acaai.org/allergies/types/food-allergies/types-food-allergy/oral-allergy-syndrome.
  7. Lomas JM, Järvinen KM. Managing nut-induced anaphylaxis: challenges and solutions. J Asthma Allergy. 2015 Oct 29;8:115-23. doi: 10.2147/JAA.S89121. PMID: 26604803; PMCID: PMC4631427. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631427/pdf/jaa-8-115.pdf.
  8. Roberts, G., Xatzipsalti, M., Borrego, L., Custovic, A., Halken, S., Hellings, P., Papadopoulos, N., Rotiroti, G., Scadding, G., Timmermans, F., Valovirta, E. Paediatric rhinitis: Position paper of the European Academy of Allergy and Clinical Immunology. Allergy. 2013 Sep;68(9):1102-16.
  9. American College of Allergy, Asthma & Immunology [Internet]. Arlington Heights, IL: American College of Allergy, Asthma & Immunology; 2014. Available from: https://acaai.org/allergies/types-allergies/food-allergy/food-allergy-avoidance.
  10. Harvard Health Publishing [Internet]. Boston, MA: Harvard Medical School; 2020. Available from: https://www.health.harvard.edu/healthbeat/6-tips-for-managing-food-allergies.
  11. Mayo Clinic [Internet]. Rochester, MN: Mayo Foundation for Medical Education and Research; 2019 Sep 14. Available from: https://www.mayoclinic.org/diseases-conditions/anaphylaxis/symptoms-causes/syc-20351468.
  12. Wright BL, Walkner M, Vickery BP, Gupta RS. Clinical Management of Food Allergy. Pediatr Clin North Am. 2015 Dec;62(6):1409-24. doi: 10.1016/j.pcl.2015.07.012. Epub 2015 Sep 7. PMID: 26456440; PMCID: PMC4960977.