Even though they’re all found in the same aisle at the grocery store, there’s one key difference between tree nuts (which include almonds, walnuts, cashews, and pistachios, to name a few) and peanuts.

I know several people that say they have a "tree nut allergy." They are not as far as I know allergic to peanuts. Can that be a real thing or more specifically a *single* real thing? I know they ...