Keep Candy and Chocolate Away from Pets
Keep holiday treats and candies out of your pets reach as they can make them quite sick.  If eaten, candy wrappers can cause an upset stomach.

Chocolate, particularly unsweetened, dark, bittersweet and baking chocolate, can be toxic to pets, especially dogs who are more prone to eat it.  If your dog eats chocolate, call your veterinarian immediately or an animal poison control center as treatment may need to be rendered immediately.  Symptoms of toxicity include excitement, nervousness, trembling, vomiting, diarrhea, excessive thirst or urination, muscle spasms, and seizures.

Keep gum, candy, or breath fresheners containing the sweetener xylitol away from your dog.  When a dog eats even a small amount of xylitol, it causes a surge of insulin, and the animals blood sugar may drop quickly and dangerously.  Cases of liver damage have also been associated with ingestion of xylitol.  If your dog ingests xylitol, contact your veterinarian or an animal poison control center immediately.

Keep Pets IN When Trick-or-Treaters Are Out
If you plan to participate in Halloween festivities keep pets in a quiet part of the house.  Pets can become overexcited, confused or frightened by trick-or-treaters in costume.

Watch for open doors and make sure your pets have ID tags and/or microchips in case they do get out.  Remind your guests that your normally friendly pet may want to be left alone.  Young trick-or-treaters may be scared of dogs who run excitedly toward them and the owner answers the door.

Outdoor pets, especially black cats, should be kept indoors on Halloween.

Decorations are Potential Tricks
Halloween decorations such as fake cobwebs should be kept out of reach of pets.  Light strands, loose wires and electric cords can be a serious hazard to your pet, especially puppies who may chew them.  Never leave candles, such as jack-o-lanterns, unattended especially around puppies and kittens.  Never allow your pets to eat a leftover jack-o-lantern, as rotted, moldy pumpkin can make them seriously ill.

Costumes May Not Be a Treat
Some pets might not mind "dressing up" for Halloween, but for others, it could be a stressful experience best avoided.  Costumes should fit properly and not hinder your pet's movement, vision, or breathing.  

Have your pet try on the costume several times before Halloween so it can get used to wearing it.