Today in the workshop .....

[Farside]

If they can eat runner beans without needing an EpiPen, then is it something to do with the processing of peanuts, not the actual 'nut'?

Yonks back, whilst in a packaging plant, I asked about this very thing.
The same machine can be packaging proper nuts one day and peanuts the next, sometimes the changeover happens sloppily and all traces of nuts aren't removed 100%.