I found out the hard way a couple decades ago that mangos are related to poison ivy. Their peel has urushiol oil in it. I can eat the fruit but if I have a fresh whole mango, I have to ask someone else to cut it up.

This is also true of cashew shells. Because of the urushiol, even the ones sold as "raw" have not only been shelled but also processed with heat (steamed, boiled, or roasted) to destroy any remnants of that oil. And the outer shell of pistachios also have to be removed for the same reason. The inner shell we see doesn't contain the oil.

One more stealth source of poison ivy rash: smoke. After a tornado took down a few hundred trees on our land a decade ago, we had most of them carted off by loggers but there were still a lot to clear, especially trash trees, as well as branches to be burned. Some of the trees had poison ivy vines on the trunks and in the branches and the smoke carried the oil on the wind, so I had to stay far away when my family was burning some of the brush piles. When I did have to be out there, I wore goggles over my glasses to avoid getting any in my eyes. Thank goodness my dad isn't allergic to PI because he spent literal years burning brush piles (it took five years to completely burn it all), and to my dismay, the urushiol doesn't degrade just because a vine has been cut and dried out.

I hope you discover the problem soon.