dogs and grapes danger ?

this is a alert put out by the ASPCA
what is in grapes that can hurt a dog?
did grapes always hurt dogs?

This is officially a WAG.
Most Net sites say feed your dog/cat grapes to actually HELP with kidney problems. So here’s my guess: the grapes and raisins may have been too many eaten at the same time, or stil affected by the pesticides which disagreed with doggie or kitty.
Aside from this, all I have is a

Another WAG here. Maybe it’s something to do with fruitarian/vegetarian pets.

Ice Wolf is right, the Web is full of references to people feeing fruit to pets with no ill effects. But you know how it goes: “If some is good, then more is better.”

This thread reminded me of how my brother-in-law used to toss green grapes one at a time to his Weimaraner, who gobbled them up eagerly. Then B-I-L would throw a green olive.