I don’t know all the details, but a cause I’m aware of is eating uncooked tomatoes, which causes them for me.
It’s actually quite common for nightshade foods in general to cause cancurs.
Some of the common ones are tomatoes, eggplant, potatoes, peppers, and tobacco. Like I mentioned, though, I don’t get them when I eat a nightshade cooked only raw, but some do get them even with cooking.
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