There is a reason why you cannot buy cashews in the shell. Cashews are poisonous if they aren’t processed properly. That’s no big surprise considering they are in the same family as poison ivy. In fact, its toxin, urushiol, is the same allergen that gives poison ivy its itch.
Cashews are grow as a hanging nut underneath a false fruit (false fruit having their seeds on the outside) sometimes referred to as “apples”. These apples grow in trees that can reach around 30 feet tall.
After being picked, the cashews are roasted to release the poisonous fluid. This leaves a wrinkled and dried skin on the cashew which is then removed.
The “cashew nutshell liquid” is sometimes collected and used in things like varnish and even fungicides.