While we call them nuts, cashews are actually seeds that grow on the outside of a fruit called the 'cashew apple.' Native to Brazil, the cashew plant is related to poison ivy. The cashew seed is encased in a double shell that contains urushiol, the same irritating oil found in poison ivy and poison oak. This is why you never see cashews sold in their shells like peanuts or walnuts. They must be roasted at high temperatures to destroy the toxins before they are safe to handle and eat. Even the 'raw' cashews sold in stores have been steamed to remove the shell. The cashew apple itself is edible and sweet but has a very thin skin, making it too fragile to export, so it is mostly consumed as juice or jam in tropical regions.