What is cashew nut shell?

Cashew nut shell refers to the outer shell that encases the cashew nut, which is the seed of the cashew tree (Anacardium occidentale). This shell is not edible and contains toxic compounds, including anacardic acid, which can cause skin irritation. The shell is often processed to extract cashew nut shell liquid (CNSL), a valuable byproduct used in various industrial applications, such as in the production of resins, lubricants, and pesticides.