Yes hogweed is poisonous and if you have hogweed in your yard or come across hogweed do not touch it because it can cause skin burns.
When hogweed is combined with moisture and sunlight the hogweed can cause severe burns on your skin and even painful blisters and although the painful blisters and severe burns can go away and subside, permanent scarring can remain.
If you happened to touch hogweed with your bare hands then you can burn your eyes as well if you touch your eyes with your hands.
Just like Poison Ivy is poisonous and should not be touched the Hogweed is much more poisonous and should not be touched or ingested.
If the Hogweed is ingested by humans and other animals it could cause severe health issues and possible death if you don't get treated.