Loud noises and strange costumes can spook the dog. Not a good idea to take it along trick or treating.
The dog should have an up-to-date a pet tag with your identification in case it gets out with the constant opening and closing of the doors.
Constant doorbell ringing and strange creatures at the door may confuse and frighten a dog. It will be safer kept in a room away from the door until the excitement is over.
Chocolate, especially dark chocolate, is toxic to animals. Hide it from the dog or send it to me.
Another danger is candy wrappers lying around because dogs don’t know that they shouldn’t eat sweet smelling paper or foil. Dogs can’t digest them and they can cause intestinal blockages.