The cashew, botanically-known as Anacardium occidentale, is the seed of a tropical evergreen plant related to the mango, pistachio, and poison ivy. Originating in Brazil, the cashew plant made its way to India in the sixteenth century via Portuguese sailors.
Unlike most fruits where the seed is found inside the flesh, the cashew seed hangs from the bottom of the cashew apple. Although the fresh cashew apple fruit is not only edible but delicious, it is only available to those who grow the plant. It is much too perishable to bring to market. Cashew apples begin to ferment as soon as they are picked and will barely last 24 hours. Cashew apples are highly prized in their growing locale, where they are sometimes found canned, in jams, or used to make liqueurs.
The kidney-shaped cashew nut is encased in a hard shell with two layers. In between these layers is a black substance called cardol, which is extremely caustic and can cause blistering of the skin upon contact. This substance is removed during the shelling process and is used in the making of such products as varnish, insecticide, paint, and even rocket lubricant. For this primary reason, cashews are never sold in the shell.