Yep onions are posinus to dogs.

when Kirby got bad sick,, the first thing the vet asked me was if i had given him onions or if i had any onions growing on my property. he asked me that more the once.

they say grapes are posinus to dogs too.
my friend has been giving her Boston Terrier grapes for years.

Kirbys has had a few and never got sick from them either.
depends on how much your dog eats i guesss.