Almost half of people who are allergic to peanuts are also allergic to tree nuts, such as almonds, Brazil nuts, walnuts, hazelnuts, macadamias, pistachios, pecans, and cashews. People who are allergic to one tree nut are often allergic to at least one other tree nut.
Tree nut reactions can be severe, even with small exposures, and research has shown that peanuts and tree nuts are the two leading causes of fatal food allergy reactions. Given these considerations, I recommend to patients that any tree nut that is skin-test positive be removed from the diet.