Cashew oil refers to oil extracted from the fruit of the cashew. The cashew nut has a shell with an oily outer layer, and a hard inner layer, within which the familiar cashew nut is contained. Cashew shell oil comes from the outer shell. It is toxic to humans, and is normally considered a waste product. Some work, however, showed that cashew shell oil can be useful in fighting dental cavities.[1] Other uses of cashew shell oil have been explored, including as an additive to brake fluid, to reduce brake fade and brake lining wear. [2]