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 Immunologyindicated 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