Never ever ever eat them. Or open them.
Let me back up for a moment. I don't mean cashews that are sold in the store as "raw" -- those are fine. In actuality, they are not raw, they are heated to break down the toxins in the nut, in the skin - how anyone ever figured out the nuts are edible once treated is beyond me. Did I just say toxins? Oh yes, toxins, specifically toxic oil. Called Cardol oil. Which is an urushiol, a catch-all for oils derived from members of the Family Anacardiaceae, the most famous members being poison ivy, poison oak, and poison sumac. Less famous urushiols include mango skin and cashews. That's right, cashews.
Maranon, the fruit of the cashew (check out my link above or the photo below to see what it looks like) is extremely tannic except for its 24 hours of ripeness, during which it must be eaten (or used for confections, ice creams, sorbets, etc) or it starts to ferment. Which may not be a bad thing. Raw, it simply tastes tannic.
But the nut is an entirely different story. Ethan was served a drink presumably made with some maranon juice, and garnished with a maranon (sorry this is out of focus, it was dark and I was a little out of sorts). The cashew is the green thing on top. Or rather, that's the cashew pod:
So now you know what the fruit and nut look like. Ethan decided he would try to open it. When he couldn't (he attempted the job with his teeth) I thought I'd flex my jaw muscles and open it up myself. Which I did:
Now looking at this photo I realize I can see the glistening oil just under the skin that caused my mouth to almost immediately burst into a painful sensation I can only describe as what eating battery acid must be like. Dinner, which arrived shortly after that, was painful for both of us - we both succeeded in getting oil on ourselves. In our mouths. Ethan deadened his pain with alcohol. I chose to freeze mine out with a non-alcoholic watermelon freeze. I could barely taste my food for the rest of the night. But I think nothing of it as soon as the sensation goes away, 16 hours later.
Flash forward two days later. I'm back in the US, sitting at home, when I notice that something is amiss on my face. All around my mouth I've broken out. I look in the mirror. My entire face is broken out in something that looks like a cross between poison ivy and excema. The next day I google cashews. I freak out. My face! My precious face!
After failing to get an appointment with my dermatologist, I called my internist. Or rather I spoke with my internist's nurse. Who took detailed notes and, after speaking with my doctor, recommended that I not come in unless it got worse. In the meantime? Hydrocortisone 1%, benadryl, and no touching!
I'll never ever ever do that again. No cashews!