They've heard from reliable sources that certain human food, like grapes or onions, are actually toxic if ingested by dogs. (aplaceforanimals.com)
There is caffeine in a large array of human products and it is toxic when ingested by cats. (cathealth.com)
When ingested in dogs and cats, it can be deadly, as it has a narrow margin of safety — that means a small amount of the drug results in severe poisoning! (petpoisonhelpline.com)