I think cashews have been scientifically proven to be the most addictive substance on earth. I tried to find the studies that must have been published on this hidden epidemic, but instead I found this:
cashews are in the same plant family as poison oak (the sumac family) — that’s why you never see them in shells, handling them would be a bad thing for anyone sensitive to sumacs. You may also have heard of “mango mouth,” a rash that results from contact with mango skin — another member of the sumac family. I’ve not heard of the sumac connection causing anyone problems from consuming cashews or mangos, but I get poison oak very easily and have been the victim of mango mouth myself, so I stay away from cashews for the most part on general principals.I was bemused to read this. I have a cashew addiction and my mum had a mango addiction…..until the day she ate a whole box of mangos in one sitting. She developed an allergic reaction to mangos that was so strong she would swell up if she just walked into a room containing a mango.
I checked in Wikipedia and indeed the cashew, mango, poison ivy and pistachios are all members of the same plant family and mango and poison ivy share a common chemical irritant.
Mountains and rivers 
I knew there was a reason why I have never liked mango. I can remember a time I didn’t like cashews either but that has long gone. Do cashews actually have a shell? I imagine them as little nodes on the roots. I don’t know why I think that but probably because you never see them in a shell and you never here of a cashew deshelling position in the jobs available.
Cashews are one of the three fruits that have the seeds on the outside (challenge: name the other two). The cashew fruit looks like a pear, and the cashew nut hangs from the bottom. Never seen one, probably have to go to India or somewhere.