Coconut is not a botanical nut; it is classified as a fruit, even though the Food and Drug Administration also recognizes coconut as a tree nut. While allergic reactions to coconut have been documented, most people who are allergic to tree nuts can safely eat coconut.
FAQ: Nutmeg is a spice that is derived from seeds, not nuts. It may be safely consumed by people with a tree nut allergy. (edited)
More on Coconut:
One of the most common questions we are asked by patients with tree nut allergy is whether coconut is a fruit or a nut. Unfortunately, the answer is a little complicated. Botanically, the coconut is classified as a fruit--more specifically, it is a drupe. Drupes are more commonly called stone fruits. Other stone fruits include peaches and nectarines; blackberries and raspberries are drupes comprised of aggregates of drupelets.
Some other common foods that are mistaken for nuts are butternut squash and water chestnuts.