People with tree nut allergy are seldom allergic to just one type of nut,[REF][REF] and are therefore usually advised to avoid all tree nuts, even though an individual may not be allergic to the nuts of all species of trees.
Someone allergic to walnuts or pecans may not have an allergy to cashews or pistachios, because the two groups are only distantly related and do not necessarily share related allergenic proteins.