I know that's a strange subject:

I have the following health problem, which only seems to occur in North America.

Eating onions, from a Subway sandwich bar, or onions in other sandwiches which have been prepared and packaged seem to cause extreme diarrhea to me, the likes of me not leaving the bathroom for almost one day.

The funny thin is, that this only happens in North America with onions which are in some prepackaged sandwiches or Subway sandwich restaurants.

On the contrary, I've never had any issues in Europe, in the Mediterranean, on various trips.

Is there a reasonable medical answer to this? or does anybody have the same issue.

Like, just onions from Subway, which are just red onions, or standard onions like you buy in the grocery store, or...? Curious as to how many "tests" of this you've had as it sounds totally random...

thanks for the answer. I've done some research. Some people seem to have an onion allergy, others an onion intolerance resulting in diarrhea. Myself I seem to be the latter.

Don't know if it's red onions or other kind of onions, it just only seems to be when I eat onions in various sandwich places and it seems more an issue "North America" vs. "Europe". At the moment I don't even dare to test of fear of spending a whole night in the bathroom. Never had any onion issues in Europe, neither the UK nor the Mediterranean.

It's likely just red onions, it's an allergic reaction. Lots of posts on various forums show others suffer from the same problem (or migraines) and it seems that red onions cause them rather than white or yellow (which are used in the UK a lot, hence why perhaps you have the problem here and didn't there).

Just avoid eating onions. It's easily done.