The problem is that B6 is hidden in many pills. The Blackmores Magnesium pills I was taking carried 50 units of B6, the Swisse Zinc pills 25 units, the Blackmores Mega B another megadose of B6, and so on ...

I think some energy drinks have it too.

The daily B6 requirement is tiny, yet people take these huge doses, many unknowingly.

The link listed by Kiwi33 is excellent, but be aware that people are reporting B6 neuropathy and high blood B6 levels on lower doses than are generally regarded as dangerous in the literature.

As well as genetic processing issues (enzymopathies) I suspect some people have genetic weakness is their nerves, which makes them vulnerable to toxic assault.