Are there any foods that are harmless when eaten alone yet are dangerous or toxic when eaten together with another otherwise innocuous food?
There can obviously be problems if you combine acidic foods with basic foods. I'm looking more for pairings that cause some sort of chemical reaction that produces a toxin and/or some pharmacological product.
This question is motivated by some claims that have been made over on Cooking.SX. For example, it is claimed that the combination of crab and persimmon is toxic.
I could have sworn that I had seen a similar question asked either here or on Cooking.SX, however, I couldn't seem to find it after doing a search.