Botanically, coconuts are most closely related to other palm and betel nuts. While botanical relationships are not the only factor that determine whether two foods will be cross-reactive, foods that are close biological relatives often share related allergenic proteins. For example, cashews and pistachios are two closely related plants that contain similar proteins. People who are allergic to one of these nuts are often allergic to the other one as well. When it comes to coconut, there is some evidence of cross-reactivity between coconuts and hazelnuts, and coconuts and walnuts.