Know your onions

I usually substitute recipes that ask for onions with echalion shallots (largest type of shallot) or spring onions, both shallots and salad onions are okay. But I have had normal onions and red onions now and again and it hasn’t had any detrimental effects for me, but then I haven’t managed to pin point any eureka moments with foods which are apparently bad. Personally I think it’s a load of shit.