The CDC suggests testing face paint on a small area on your arm. That way you can see if it irritates your skin before you slather it everywhere.
Skin around your eyes is extremely sensitive, so check labels on face paint or makeup. If it says avoid applying by your eyes -- even if the people on the package are doing the opposite -- follow the directions.
Throw away makeup that smells bad, as it may be contaminated.
If your inner devil prefers a mask, wipe it down before wearing it. You likely weren't the first to try it on in the store.
CNN Newsource affiliate KTVK took more than a dozen masks to be tested. Even the biologist was shocked by how many germs and molds he found.
"In terms of gross, this is particularly disgusting," said Stan Kikkert, a biologist from Mesa Community College.
The microscopic monsters can cause infections. Alcohol should disinfect properly. Pay particular attention to the nose and mouth.
4. Just because Michael Jackson wore them ...
Color contacts made Michael Jackson look extra spooky in "Thriller," but unless you've got a prescription, don't wear them. Some stores do sell them, but that's illegal without a prescription.
Optometrists warn the contacts aren't one-size-fits-all.
"Wearing lenses that don't fit properly can suffocate the eye, causing irritation and infection," Dr. Christopher Coad, director of Chelsea Eye Associates in New York, said in a statement. "Bad infections can even lead to blindness and/or loss of the eye."
If you want to wear them, get a prescription.
5. Don't let chocolate go to the dogs
If you dress up your pet, make sure the costume lets them breathe and move. Avoid costumes with small parts they might swallow.
Speaking of eating, chocolate may be a favorite in your goodie bag, but it can be deadly to dogs and cats.
Pet insurance company Petplan sees 25 percent more claims during Halloween -- more than any other week in the year.
Swallowed wrappers and lollipop sticks can cause blockages that might not be noticed for days.
The darker the chocolate, the deadlier it is to your pet, according to Dr. Ron DeHaven with the American Veterinary Association.
"When kids come home after a night of trick or treating and dump their bag of candy, be sure that your pets are safely away in another room away from your kid's loot," DeHaven said. Store it somewhere where your pet can't get to it.
If pets do get hold of chocolate, call your vet immediately. The ASPCA has a poison hot line, too: 888-426-4435.