Market Overview Almonds, Brazil nuts, cashews, hazelnuts, pecans, pistachios, and walnuts are different kinds of tree nuts. An allergy to anyone tree nut does not always imply that the person is allergic to all tree nuts. Nonetheless, some tree nuts are closely related, such as cashew, pistachio, pecan, and walnut. The seeds borne by the individual fruit-bearing trees are known as tree nuts....