As many as 1.8 million Americans are allergic to tree nuts, which are among the leading causes of fatal reactions to food including anaphylaxis. Tree nuts include walnuts, almonds, hazelnuts, cashews, pistachios and Brazil nuts. (Coconuts cause some confusion. Technically they are drupes, but the FDA has classified them as tree nuts.) Tree nuts can be found in salad dressings, honey, pancakes, pasta, veggie burgers and even in barbecue sauce. They are not to be confused with peanuts, which are legumes.