I have a pen pal in Brazil (is it still a pen pal if we e-mail? anyway...) and knowing that I like nuts sent me some cashews. Apparently there is a cashew farm near enough to her that she went right to the source and procured me some raw nuts. I've eaten a few handfuls; the taste is a little more sharp than I'm used to, but in a good way, I have however had some serious discomfort after eating them. I'm not allergic to nuts in general or cashews specifically so I thought I would ask about it before ingesting any more. Anybody have any ideas or thoughts?
Nuts can go rancid. I've also had stale nuts, pecans or peanuts that were exposed to too much humidity. This adversely affects the texture. They need to be fresher than that.
Cashews, however, are in a slightly different boat. See Anacardium occidentale L.
Cashews have a toxin in their shells that resembles poison ivy. When harvested, cashews are roasted in their shells to reduce the toxin and make the shells brittle and easy to remove.
If these cashews were harvested by an amateur this process might have not been done correctly and you may be reacting to the toxin.
Truly raw cashews are not safe to eat. The "raw" cashews in stores are actually slightly steamed.
Roasting the nuts should neutralize the urushiol remaining in them (I'm assuming they're not still in their outer shells).
Also, technically, cashews aren't "nuts". It's the seed of a fruit.
You can eat the fruit of the cashew off of the tree, called the "cashew apple" and it is supposed to be popular in places where it grows and has a mild sweet flavor, but it's never seen anywhere else because it's very soft and doesn't transport at all. In places where they grow, they are purportedly a popular as juice and an ingredient in smoothies in markets. If you do not have cashews growing where you live, you might be able to find cashew juice in bottles or cans.
The nut you cannot eat off of the tree because the shell contains urushiol and is usually removed by roasting them in fires (don't be downwind of these fires as they are irritating to skin and lungs--understatement). The nut or seed itself is quite safe once the shell has been removed, since it's only the shell that contains the toxin, but that is why you never find cashews to buy in the shell.
Most kinds of nuts and seeds are certainly better the fresher you can get them because the oils contain large amounts of mono- and poly-unsaturated oils which are subject to oxidation over time and become less tasty and less healthy after they are oxidized (go rancid). The exceptions being so-called tropical nuts/oils--palm and coconut--which are almost entirely saturated (contain almost no double bonds) and are therefore much less subject to oxidation/becoming rancid, and therefore keep better than other oils.
When visiting Cost Rica, my tour guide pointed out a cashew tree in a park with fruit on it. I asked if it was safe to eat and she looked at me funny and said, "Yeah, but I don't know why you'd want too." I took a bite of the apple and ate the nut. They were OK. for the rest of the day I had a burning sensation all around my lips like a hot chili pepper sensation. In general I have very low sensitivity to poison ivy, I used to remove the stuff from my yard bare handed before someone told me what it was. So I wouldn't recommend anyone eat truly raw cashews.