Americans will spend nearly $7 billion on Halloween costumes and masks this year, but it's the tiny little monsters living on those masks that are enough to make anyone scream.

With so many people touching, breathing and sweating underneath those masks, you may wonder how clean they are.

An Arizona television station bought nearly a dozen rubber masks, swabbed the nose and mouth areas, and took the samples to Bio-Tech Expert Dr. Stan Kikkert for testing.

"I was quite surprised at the number of bacteria, the diversity of the bacteria and the number of bacteria that you guys found on these different plates," said Kikkert.

As it turns out, every mask was full of living bacteria and germs. The devil mask was found to be the worst, and had microscopic "creepy crawlers" like mold and fungi.

"One person after another, after another adds to this and allows these bacteria to cultivate," Kikkert said. "Why we see some much robust results."

Kikkert said he'd recommend a mask that covers just the eyes, leaving your mouth and nose clear, but if you are going to buy a rubber mask, soak it in rubbing alcohol to kill the germs.