They're possum grapes, and they are not poisonous, they actually make a very nice jelly.
Some people do have reactions to the Solanus family of plants.
Nightshade, potatoes, tomatoes, bell peppers.
It is interesting. Here near Seattle, there is a black nightshade plant that has flowers that look EXACTLY like tomato flowers. They produce fruit - berries of sorts - that are a bit bigger than pea sized and a dark purplish color, almost black.
Being a daredevil type, I’ve actually eaten a few of them. They have a bit of a tomato flavor, and are mildly sweet.
Never have been able to find out if fur sure they are poisonous.
Most plants, probably 97%, are actually edible, although they might give you the chits for a few days. But there is a small percentage that if you have them for breakfast, you will never eat dinner. Ever. Oleander comes to mind, a highly, highly lethal plant.
They're possum grapes, and they are not poisonous, they actually make a very nice jelly.