system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why chocolate is harmful to dogs?

I've also heard grapes are bad for them too?
gpt
Chocolate contains a chemical called theobromine. Humans can easily metabolize theobromine, so you would need to eat a monumental amount of chocolate before you would suffer any consequences.

Dogs don't metabolize theobromine at the same rate humans do, and it is possible for a dog to eat a modest amount of chocolate, and get theobromine (chocolate) poisoning.