The American Veterinary Medical Association recommends:
1) Keep pets inside. Especially cats, especially black ones.
2) Pets should have a microchip ID if they happen to escape the house and go missing, this may help them to be returned safely.
3)No candy for pets, especially Xylitol-sweetened products which are extremely toxic for dogs, as is chocolate.
4) Keep candles, jack-o-lanterns, glow sticks, bowls of candy securely out of pets reach where they can’t be knocked down.
5) Pets that are leery of strangers or who might bit should be locked away from the front door during trick or treating hours.
6) Costumes for pets can be a lot of fun but:
a) make sure it fits properly, is comfortable and doesn’t interfere with breathing, eyesight etc..
b) make sure the pet is accustomed to being costumed before Halloween.
c) make sure parts of the costume can’t easily be bitten off and swallowed.
d) never leave a pet unsupervised while it is wearing a costume.
A Halloween safety video can be seen on YouTube https://www.youtube.com/watch?v=8JC8LDtCBYQ