What is one poison to werewolves?

There is no scientifically recognized poison that specifically targets werewolves, as werewolves are fictional creatures.

However, in many fictional works, silver is often depicted as a substance that is harmful or even deadly to werewolves. This is a common trope in werewolf mythology and folklore, and it's often used in stories to give humans a way to fight back against these creatures.

It's important to remember that this is purely fictional and has no basis in reality.