Rare? Uhhh this happened to me a few years ago. We bought some dehydrated shiitake mushrooms from Costco. They were absolutely delicious and I ate a handful of them.

Within about 4 hours I had red hive like marks all over my body and it hurt to wear any clothing or touch anything. The pain was absolutely excruciating and nothing dulled it. My doctor said it was mushroom toxicity and I would just have to “wait it out”. Well that took about 6 days to get it out of my system.

To this day I have avoided eating any mushrooms raw.

[–] tesseract@beehaw.org 1 points 11 months ago

Costco shiitake mushrooms shouldn't be toxic at all. Otherwise, so many would be dead by now - at least a few people would have eaten too much before the toxicity showed up. Perhaps you are badly allergic to it? That happens to a few people to common and safe food.