Tree nuts include macadamia nuts, brazil nuts, cashews, almonds, walnuts, pecans, pistachios, chestnuts, beechnuts, hazelnuts, pine nuts (pignoli or pinon), gingko nuts and hickory nuts. Like peanut and shellfish allergies, a tree nut allergy tends to be severe, and is strongly associated with anaphylaxis. Walnuts and cashews are the two tree nuts that cause the most allergic reactions. At least 90 percent of children diagnosed with tree nut allergies will have them for life.
Cross-Reactivity Among Tree Nuts:
Most people with tree nut allergies are not allergic to all tree nuts. However, there is high cross-reactivity among various families of tree nuts. About 12 percent of people who are allergic to one tree nut are allergic to another tree nut. The strongest probability of cross-reactivity is between walnut and pecan, and between cashew and pistachio; however, many tree nuts have some possibility of cross-reaction between each other. For this reason, people who are allergic to one type of tree nut are generally advised to avoid all tree nuts as a precaution.
Cross-Reactivity Between Tree Nuts and Peanuts:
Peanuts are legumes, and are biologically unrelated to tree nuts. However, there is a high level of allergic cross-reactivity between peanuts and tree nuts, meaning that people with tree nut allergies are at increased risk of developing peanut allergies. If you are diagnosed with a tree nut allergy, your allergist will advise you whether to avoid peanuts as well.
Tree Nut Allergy Symptoms:
The most significant symptom of tree nut allergies is anaphylaxis, a systemic reaction that can cause shock, severe breathing difficulties, and cardiac arrythmia, among other symptoms. Because tree nut allergies are especially likely to cause anaphylaxis, people with tree nut allergies will be prescribed injectible epinephrine (an Epi-Pen or similar medicine) and should always carry it with them.
Other common symptoms of tree nut allergies are skin symptoms (like hives and welts) and asthma.
Coconut and Tree Nut Allergies:
Whether coconut should be considered a tree nut is a matter of some controversy. The FDA mandates that coconut be considered a tree nut for labeling purposes; however, as the Food Allergy and Anaphylaxis Network notes, coconut allergies are exceedingly rare, with fewer than 10 reported cases. A June 2007 study in the Annals of Allergy, Asthma, and Immunology indicated cross-reactivity between coconuts, walnuts, and hazelnuts in one patient. Your allergist can advise you on the suitability of coconut for your diet.
Foods Commonly Containing Tree Nuts:
Foods always or almost always containing tree nuts include:
- Pesto (unless specially prepared without pine nuts)
- Nut liqueurs (Frangelico, Amaretto, and Nocello)
Foods that commonly contain tree nuts include:
- Granola bars
- Trail mix
- Ice cream
- Candy bars
- Baked goods
Labeling Laws and Tree Nut Allergies:
Tree nuts are one of the "big eight" most common food allergies, and as such, the FDA requires manufacturers selling foods in America to label foods containing tree nuts. The Food Allergy Labeling and Consumer Protection Act requires that manufacturers label which tree nut is in a given product.
Manufacturers are not required to mention the presence of tree nuts on manufacturing lines. Many do, however, due to consumer pressure. Because of the possibility of anaphylaxis, people with tree nut allergies should avoid products that mention the possibility of tree nut cross-contamination on labels.
Eating Out with Tree Nut Allergies:
While tree nuts are not as prevalent as many other allergens, the risk of anaphylaxis makes them dangerous to eat out with at restaurants with any chance of cross-contamination, so call ahead and discuss your diet with a manager or the chef.
The riskiest cuisine for nut allergies is Greek; several common dishes use walnuts. Cashews are used in Chinese cuisine, while almonds feature in Mediterranean food. Pesto, with pine nuts, is likely to appear on Italian menus. And many higher-end restaurants make vinaigrette dressings using tree nut oils. Japanese and Latin American are likely among the safer ethnic cuisines.
Tree Nut Allergies and Anaphylaxis:
Peanut allergies are popularly considered the most severe allergies, and it's true that both peanut and shellfish allergies cause far more cases of anaphylaxis than tree nut allergies. But both of those allergies are much more common. The fact is that there is strong evidence that severe reactions are far more likely to occur in people with tree nut allergies --- especially cashew allergies --- than with peanut allergies. For this reason, it's essential that anyone with a tree nut allergy learn the symptoms of anaphylactic shock and carry injectible epinephrine at all times.
Living with Tree Nut Allergies:
Management of tree nut allergies depends on strict avoidance of tree nuts. For young children, this can depend on the collaboration of a wide variety of interested adults: parents, caregivers, school teachers and administrators, and parents of close friends. There are some places, however, where it may be especially difficult to avoid tree nuts. These include parties (where bowls of mixed nuts may be served) and bars.
Nut allergies are a well-recognized cause of severe allergic symptoms, and so families dealing with tree nut allergies are likely to find at least some systems in place for dealing with severe allergies in many institutions. Here are some resources you may find useful:
- Does Your Child Need a 504 Plan?
- Airline Travel with Food Allergies
- Tips for Eating Out with Food Allergies
- Traveling with Food Allergies
- Grocery Shopping for Food Allergies
Anyone with a tree nut allergy (or caring for a child with a tree nut allergy) should be thoroughly briefed on reading labels and on the symptoms of severe food allergies.
Benito, Cristina, et al. "Identification of a 7S Globulin as a Novel Coconut Allergen." Annals of Allergy, Asthma & Immunology. Jun. 2007 98(6): 580-84.
Clark, A. T., et al. "Cashew Nut Causes More Severe Reactions than Peanut: Case-Matched Comparison in 141 Children." Allergy. Aug. 2007 62(8) 913-16.
Clark, Andrew T., and Pamela W. Ewan. "The Development and Progression of Allergy to Multiple Nuts at Different Ages." Pediatric Allergy and Immunology. Sep. 2005 16(6): 507-11.
Davoren, M., and J. Peake. "Cashew Nut Allergy is Associated with a High Risk of Anaphylaxis." Archives of Disease in Childhood. 2005(90): 1084-85. 5 Jul 2007.
de Leon, M. P., et al. "Immunological Analysis of Allergenic Cross-Reactivity Between Peanut and Tree Nuts." Clinical and Experimental Allergy. Sep. 2003 33(9): 1273-80.
Fleischer, David M., et al. "The Natural History of Tree Nut Allergy." Journal of Allergy and Clinical Immunology. Nov. 2005 116(5): 1087-93.
Fleischer, J.M. "The Natural History of Peanut and Tree Nut Allergy." Current Allergy and Asthma Reports. Jun. 2007 7(3): 175-81.
Goetz, David W., et al. "Cross-Reactivity Among Edible Nuts: Double Immunodiffusion, Crossed Immunoelectrophoresis, and Human Specific IgE Serologic Surveys." Jul. 2005 95(1): 45-52. 8 Jul. 2007.