I have included some great advice from The Toronto Humane Society:

Halloween is a time for fun, mystery and make believe.  As many of us get ready to join in the festivities and open our homes to trick-or-treaters, The Toronto Humane Society would like to share some important safety tips for pet parents to follow leading up to October 31.

Unlike us, pets do not revel in the celebrations of Halloween and can become nervous. Costumes, decorations, loud noises and frequent visitors to the front door can cause anxiety in our pets.

Provide your pet with a safe place. Pets should not be in the room or near the door when trick-or-treaters visit; seeing someone in a scary costume could cause your pet anxiety and she/he could easily bolt out the door.

Prepare a safe place ahead of time and introduce your pet to the area. If you have a crate, your dog may find it more comforting. You may wish to keep your cat in a room, where people are not coming in and out, for a few hours until the kids are finished trick-or-treating.

All pets should wear proper identification. ID tags and microchips, with current information, are essential. Even indoor pets should wear id in case they slip out during frequent visits by trick-or-treating kids. If your pet is not wearing identification and escapes, the chances of finding her/him decreases  dramatically.

Re-think bringing your dog or other pet out during Halloween as your pet could become frightened, lost, or injured. Walk your dog before the sun begins to set so she/he is settled at home once people prepare to set off for tricks and treats. Sadly, pets are often victims of cruel pranksters, especially on Halloween. Black cats are particularly vulnerable.

Pet costumes may seem like a cute idea, but if they are too restrictive or uncomfortable, they can cause unnecessary stress. If your pet is not happy being dressed up, respect her/his boundaries and remove the costume.

Do not surprise your pet with your own costume. Familiar people become scary when wearing costumes and masks. If you plan to wear a costume, introduce your pet to the disguise prior to putting it on; display the costume so your pet can see it, and then give your pet a tasty treat so a positive association is established.

Halloween treats like candy, candles, pumpkins, make-up and decorations can be dangerous if ingested so it’s important to keep an eye on your pet.