sounds like a allergy to oil of bergamot.
Coincidentally, I had occasion to post this in another thread just a couple of days ago: https://journals.sagepub.com/doi/full/10.1177/14034948219902...
Black tea contains a lot of fluorine, so if you're drinking a gallon a day, you're deep into hyperfluorosis territory.
Bergamot contains a chemical, a sort of terpene, aptly named "bergamottin." https://en.wikipedia.org/wiki/Bergamottin
Bergamottin famously inhibits a major liver enzyme inelegantly named CYP3A4. CYP3A4 is responsible for metabolizing a huge number of drugs and other substances. (e.g., endogenous steroid hormones.) This is what's responsible for the "grapefruit juice effect." https://en.wikipedia.org/wiki/Grapefruit%E2%80%93drug_intera...
Bergamottin also inhibits CYP1A1, which metabolizes theophylline, and CYP1A2, which metabolizes caffeine.
The most likely possibility is that consuming that much bergamottin, together with caffeine, disrupted the metabolism of the latter, leading to caffeine-induced toxicity in skeletal/cardiac muscle. (Cramps, fasciculations, etc.)
But it could also be that the inhibition of CYP3A4 messed with the metabolism of something else the man was ingesting.
I'm so curious how this effects dental health in people where daily tea drinking is common. tea stains your teeth a bit but does it also strengthen enamel with the flouride?
This case is also from 20 years ago so I do think that it was real bergamot.