I grew up using red onion (bermuda, purple) for salads, sandwiches or anywhere I wanted raw but fairly mild. I've lived all around the country too and no problems with onions until coming to the South. Now I can't trust red/purple onions at all--they'll be sharper and more pungent than yellow or white.
I really miss having a somewhat mild onion on a tomato sandwich or in a salad, but I haven't been able to figure out what's safe. (They sell a lot of sweet onions here, but I don't want a sweet taste.) We've tried buying them from different stores too, but the ones we recently got at Whole Foods were actually the most stinging to the eyes I've experienced in a long time. The kitchen stunk for days, and they were inedible on a salad.
Why would red onions be stronger here than what I've had elsewhere around the country?